Thermal energy storage system coupled with steam cracking system

ABSTRACT

An energy storage system (TES)converts variable renewable electricity (VRE) to continuous heat at over 1000° C. Intermittent electrical energy heats a solid medium. Heat from the solid medium is delivered continuously on demand. Heat delivery via flowing gas establishes a thermocline which maintains high outlet temperature throughout discharge. The delivered heat which may be used for processes including power generation and cogeneration. In one application, the energy storage system provides higher-temperature heat to a steam cracking furnace system for converting a hydrocarbon feedstock into cracked gas, thereby increasing the efficiency of the temperature control.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 18/144,134, filed May 5, 2023¹. This applicationalso claims priority under 35 USC § 119(e) to:

-   U.S. Provisional Patent Application No. 63/347,987 filed on Jun. 1,    2022,-   U.S. Provisional Patent Application No. 63/378,355 filed on Oct. 4,    2022,-   U.S. Provisional Patent Application No. 63/427,374 filed on Nov. 22,    2022,-   U.S. Provisional Patent Application No. 63/434,919 filed on Dec. 22,    2022, and-   U.S. Provisional Patent Application No. 63/459,540 filed on Apr. 14,    2023, ¹ . . . which is a Continuation in part of U.S. patent    application Ser. No. 18/171,602, filed Feb. 20, 2023, which is a    Divisional of U.S. patent application Ser. No. 17/650,522 filed Feb.    9, 2022 and patented as U.S. Pat. No. 11,585,243, and is a    continuation-in-part of U.S. patent application Ser. No. 18/142,564,    filed May 2, 2023, which claims priority from Provisional    Application 63/459,540 filed Apr. 14, 2023, Provisional Application    63/434,919, filed Dec. 22, 2022, Provisional Application 63/427,374,    filed Nov. 22, 2022, Provisional Application 63/378,355, filed Oct.    4, 2022, Provisional Application 63/347,987, filed Jun. 1, 2022, and    Provisional Application 63/338,805, filed May 5, 2022, and    Provisional Application 63/337,562, filed May 2, 2022 and is a    Continuation-in-part of U.S. patent application Ser. No. 17/668,333,    filed Feb. 9, 2022, which claims priority to PCT/US2021/061041,    filed Nov. 29, 2021 and is a continuation of U.S. patent application    Ser. No. 17/537,407, filed Nov. 29, 2021 (U.S. Pat. No. 11,603,776),    both of which claim priority from Provisional Application    63/231,155, filed Aug. 9, 2021, Provisional Application 63/170,370,    filed Apr. 2, 2021, Provisional Application 63/165,632, filed Mar.    24, 2021, Provisional Application 63/155,261, filed Mar. 1, 2021,    and Provisional Application 63/119,443, filed Nov. 30, 2020.

The contents of these priority applications are incorporated byreference in their entirety and for all purposes.

BACKGROUND Technical Field

The present disclosure relates to thermal energy storage and utilizationsystems. More particularly, the present disclosure relates to an energystorage system that stores electrical energy in the form of thermalenergy, which can be used for the continuous supply of hot air, carbondioxide (CO₂), steam or other heated fluids, for various applicationsincluding the supply of heat for power generation. More specifically,the energy storage system provides higher-temperature heat to a steamcracking furnace system for converting a hydrocarbon feedstock intocracked gas, thereby increasing the efficiency of the temperaturecontrol. New disclosure in this application (beyond what was disclosedin the parent application Ser. No. 17/668,333) appears primarily atparagraphs [32-44], [52-56], [66-881], and [178-219], and in FIGS. 7-17.

Related Art

I. Thermal Energy Systems

A. Variable Renewable Electricity

The combustion of fossil fuels has been used as a heat source in thermalelectrical power generation to provide heat and steam for uses such asindustrial process heat. The use of fossil fuels has various problemsand disadvantages, however, including global warming and pollution.Accordingly, there is a need to switch from fossil fuels to clean andsustainable energy.

Variable renewable electricity (VRE) sources such as solar power andwind power have grown rapidly, as their costs have reduced as the worldmoves towards lower carbon emissions to mitigate climate change. But amajor challenge relating to the use of VRE is, as its name suggests, itsvariability. The variable and intermittent nature of wind and solarpower does not make these types of energy sources natural candidates tosupply the continuous energy demands of electrical grids, industrialprocesses, etc. Accordingly, there is an unmet need for storing VRE tobe able to efficiently and flexibly deliver energy at different times.

Moreover, the International Energy Agency has reported that the use ofenergy by industry comprises the largest portion of world energy use,and that three-quarters of industrial energy is used in the form ofheat, rather than electricity. Thus, there is an unmet need forlower-cost energy storage systems and technologies that utilize VRE toprovide industrial process energy, which may expand VRE and reducefossil fuel combustion.

B. Storage of Energy as Heat

Thermal energy in industrial, commercial, and residential applicationsmay be collected during one time period, stored in a storage device, andreleased for the intended use during another period. Examples includethe storage of energy as sensible heat in tanks of liquid, includingwater, oils, and molten salts; sensible heat in solid media, includingrock, sand, concrete and refractory materials; latent heat in the changeof phase between gaseous, liquid, and solid phases of metals, waxes,salts and water; and thermochemical heat in reversible chemicalreactions which may absorb and release heat across many repeated cycles;and media that may combine these effects, such as phase-changingmaterials embedded or integrated with materials which store energy assensible heat. Thermal energy may be stored in bulk underground, in theform of temperature or phase changes of subsurface materials, incontained media such as liquids or particulate solids, or inself-supporting solid materials.

Electrical energy storage devices such as batteries typically transferenergy mediated by a flowing electrical current. Some thermal energystorage devices similarly transfer energy into and out of storage usinga single heat transfer approach, such as convective transfer via aflowing liquid or gas heat transfer medium. Such devices use“refractory” materials, which are resistant to high temperatures, astheir energy storage media. These materials may be arranged inconfigurations that allow the passage of air and combustion gasesthrough large amounts of material.

Some thermal energy systems may, at their system boundary, absorb energyin one form, such as incoming solar radiation or incoming electricpower, and deliver output energy in a different form, such as heat beingcarried by a liquid or gas. But thermal energy storage systems must alsobe able to deliver storage economically. For sensible heat storage, therange of temperatures across which the bulk storage material—the“storage medium”—can be heated and cooled is an important determinant ofthe amount of energy that can be stored per unit of material. Thermalstorage materials are limited in their usable temperatures by factorssuch as freezing, melting, softening, boiling, or thermally drivendecomposition or deterioration, including chemical and mechanicaleffects.

Further, different uses of thermal energy—different heating processes orindustrial processes—require energy at different temperatures.Electrical energy storage devices, for example, can store and returnelectrical energy at any convenient voltage and efficiently convert thatvoltage up or down with active devices. On the other hand, theconversion of lower-temperature heat to higher temperatures isintrinsically costly and inefficient. Accordingly, a challenge inthermal energy storage devices is the cost-effective delivery of thermalenergy with heat content and at a temperature sufficient to meet a givenapplication.

Some thermal energy storage systems store heat in a liquid that flowsfrom a “cold tank” through a heat exchange device to a “hot tank” duringcharging, and then from the hot tank to the cold tank during discharge,delivering relatively isothermal conditions at the system outlet duringdischarge. Systems and methods to maintain sufficient outlet temperaturewhile using lower-cost solid media are needed.

Thermal energy storage systems generally have costs that are primarilyrelated to their total energy storage capacity (how many MWh of energyare contained within the system) and to their energy transfer rates (theMW of instantaneous power flowing into or out of the energy storage unitat any given moment). Within an energy storage unit, energy istransferred from an inlet into storage media, and then transferred atanother time from storage media to an outlet. The rate of heat transferinto and out of storage media is limited by factors including the heatconductivity and capacity of the media, the surface area across whichheat is transferring, and the temperature difference across that surfacearea. High rates of charging are enabled by high temperature differencesbetween the heat source and the storage medium, high surface areas, andstorage media with high heat capacity and/or high thermal conductivity.

Each of these factors can add significant cost to an energy storagedevice. For example, larger heat exchange surfaces commonly require 1)larger volumes of heat transfer fluids, and 2) larger surface areas inheat exchangers, both of which are often costly. Higher temperaturedifferences require heat sources operating at relatively highertemperatures, which may cause efficiency losses (e.g. radiation orconvective cooling to the environment, or lower coefficient ofperformance in heat pumps) and cost increases (such as the selection anduse of materials that are durable at higher temperatures). Media withhigher thermal conductivity and heat capacity may also require selectionof costly higher-performance materials or aggregates.

Another challenge of systems storing energy from VRE sources relates torates of charging. A VRE source, on a given day, may provide only asmall percentage of its energy during a brief period of the day, due toprevailing conditions. For an energy storage system that is coupled to aVRE source and that is designed to deliver continuous output, all thedelivered energy must be absorbed during the period when incoming VRE isavailable. As a result, the peak charging rate may be some multiple ofthe discharge rates (e.g., 3-5×), for instance, in the case of a solarenergy system, if the discharge period (overnight) is significantlylonger than the charge period (during daylight). In this respect, thechallenge of VRE storage is different from, for example, that of heatrecuperation devices, which typically absorb and release heat at similarrates. For VRE storage systems, the design of units that can effectivelycharge at high rates is important and may be a higher determinant oftotal system cost than the discharge rate.

C. Thermal Energy Storage Problems and Disadvantages

The above-described approaches have various problems and disadvantages.Earlier systems do not take into account several critical phenomena inthe design, construction, and operation of thermal energy storagesystems, and thus does not facilitate such systems being built andefficiently operated. More specifically, current designs fail to address“thermal runaway” and element failure due to non-uniformities in thermalenergy charging and discharging across an array of solid materials,including the design of charging, discharging, and unit controls toattain and restore balances in temperature across large arrays ofthermal storage material.

Thermal energy storage systems with embedded radiative charging andconvective discharging are in principle vulnerable to “thermal runaway”or “heat runaway” effects. The phenomenon may arise from imbalances,even small imbalances, in local heating by heating elements and incooling by heat transfer fluid flow. The variations in heating rate andcooling rate, unless managed and mitigated, may lead to runawaytemperatures that cause failures of heaters and/or deterioration ofrefractory materials. Overheating causes early failures of heatingelements and shortened system life. In Stack, for example, the bricksclosest to the heating wire are heated more than the bricks that arefurther away from the heating wire. As a result, the failure rate forthe wire is likely to increase, reducing heater lifetime.

One effect that further exacerbates thermal runaway is the thermalexpansion of air flowing in the air conduits. Hotter air expands more,causing a higher outlet velocity for a given inlet flow, and thus ahigher hydraulic pressure drop across the conduit, which may contributeto a further reduction of flow and reduced cooling during discharge.Thus, in successive heating and cooling cycles, progressively less localcooling can occur, resulting in still greater local overheating.

The effective operation of heat supply from thermal energy storagerelies upon continuous discharge, which is a particular challenge insystems that rely upon VRE sources to charge the system. Solutions areneeded that can capture and store that VRE energy in an efficient mannerand provide the stored energy as required to a variety of uses,including a range of industrial applications, reliably and withoutinterruption.

Previous systems do not adequately address problems associated with VREenergy sources, including variations arising from challenging weatherpatterns such as storms, and longer-term supply variations arising fromseasonal variations in VRE generation. In this regard, there is an unmetneed in the art to provide efficient control of energy storage systemcharging and discharging in smart storage management. Current designs donot adequately provide storage management that considers a variety offactors, including medium-term through short-term weather forecasts, VREgeneration forecasts, and time-varying demand for energy, which may bedetermined in whole or in part by considerations such as industrialprocess demand, grid energy demand, real-time electricity prices,wholesale electricity market capacity prices, utility resource adequacyvalue, and carbon intensity of displaced energy supplies. A system isneeded that can provide stored energy to various demands thatprioritizes by taking into account these factors, maximizing practicalutility and economic efficiencies.

There are a variety of unmet needs relating generally to energy, andmore specifically, to thermal energy. Generally, there is a need toswitch from fossil fuels to clean and sustainable energy. There is alsoa need to store VRE to deliver energy at different times in order tohelp meet society's energy needs. There is also a need for lower-costenergy storage systems and technologies that allow VRE to provide energyfor industrial processes, which may expand the use of VRE and thusreduce fossil fuel combustion. There is also a need to maintainsufficient outlet temperature while using lower-cost solid media.

Still further, there is a need to design VRE units that can be rapidlycharged at low cost, supply dispatchable, continuous energy as requiredby various industrial applications despite variations in VRE supply, andthat facilitate efficient control of charging and discharging of theenergy storage system.

II. Steam Cracking Applications

A. Steam Cracking Concepts and Methods

Steam cracking is a widely used process in the petrochemical industry toproduce a variety of chemicals, including ethylene and propylene, whichare used as the building blocks for plastics, rubber, and othermaterials. The process involves the thermal decomposition ofhydrocarbons at high temperatures and is typically carried out in acracking furnace or coil. The operation of a steam cracking system canbe broken down into several key steps. First, a feedstock ofhydrocarbons, typically derived from crude oil or natural gas, isprepared and mixed with steam. The steam helps to control the reactionand prevent the formation of unwanted by-products. The mixture is thenfed into a furnace or coil, where it is heated to high temperatures,typically around 850° C.

The heat from the furnace breaks the chemical bonds in the heavyhydrocarbons, resulting in the formation of smaller molecules, includingethylene, propylene, and other by-products. The reaction is highlyexothermic, meaning that it releases heat, and the high temperaturesrequired for the reaction to proceed are maintained by the heat releasedby the reaction itself.

Once the cracking reaction is complete, the mixture is rapidly cooledusing a quenching agent, such as water or a quench oil. This step iscritical to stopping the reaction and preventing further unwantedby-product formation. The cooled reaction mixture is then separated intodifferent components, including the desired products (ethylene,propylene, etc.) and any by-products or unreacted feedstock.

The separated products may then be further purified to remove impuritiesand achieve the desired product quality. Any unreacted feedstock orby-products may be recycled back into the process as burner fuel tomaximize the overall energy efficiency of the process. While steamcracking is a highly efficient and versatile process, it does have somelimitations and drawbacks. The high temperatures required for thereaction to proceed mean that the process can be energy-intensive andrequire significant amounts of fuel or electricity. The process can alsoproduce large amounts of greenhouse gases, contributing to climatechange.

B. Steam Cracking Unit

The operation of a steam cracking unit can be divided into several keysteps. First, the hydrocarbon feedstock is prepared by removingimpurities and contaminants, such as sulfur and nitrogen compounds,which can interfere with the cracking reaction. The feedstock may bepreheated before it is then mixed with dilution steam, which helps tocontrol the reaction and prevent the formation of unwanted by-products.

The mixture of hydrocarbons and steam is then fed into a furnace orcracking coil, where it is heated to high temperatures. The furnace istypically lined with refractory materials, which can withstand the hightemperatures and corrosive environment of the cracking process. Themixture of hydrocarbons and steam is heated by burners or other heatsources, and the heat released by the cracking reaction itself helps tomaintain the high temperatures required for the process to proceed.

As the mixture of hydrocarbons and steam passes through the furnace orcoil, the chemical bonds in the hydrocarbons are broken, resulting inthe formation of smaller molecules, including ethylene, propylene, andother by-products. The reaction is highly exothermic, meaning that itreleases heat, and the high temperatures required for the reaction toproceed are maintained by the heat released by the reaction itself.

Once the cracking reaction is complete, the mixture of products andby-products is rapidly cooled using a quenching agent, such as water ora hydrocarbon stream. This step is critical to stopping the reaction andpreventing further unwanted by-product formation. The cooled mixture isthen separated into different components, including the desired products(ethylene, propylene, etc.) and any by-products or unreacted feedstock.The separated products may then be further purified to remove impuritiesand achieve the desired product quality. Any unreacted feedstock orby-products may be recycled back into the process to maximize the yieldof desired products.

C. Problems and Disadvantages of Steam Cracking

One of the most significant environmental impacts of steam cracking isits contribution to greenhouse gas emissions. The process releases largeamounts of carbon dioxide and other greenhouse gases, which contributeto climate change. This has become a growing concern in recent years, asthe world seeks to reduce its carbon footprint and transition to a moresustainable energy system.

From a technological perspective, steam cracking has some limitationsand drawbacks. The high temperatures and energy requirements of theprocess make it relatively expensive and energy intensive. As a result,there is a constant drive to develop more efficient and cost-effectivetechnologies to reduce the energy consumption and environmental impactsof the process.

SUMMARY

The example implementations advance the art of thermal energy storageand enable the practical construction and operation of high-temperaturethermal energy storage systems which are charged by VRE, store energy insolid media, and deliver high-temperature heat.

I. Thermal Energy Storage System

This Section I of the Summary relates to the disclosure as it appears inU.S. patent application Ser. No. 17/668,333, of which this applicationis a continuation-in-part.

Aspects of the example implementations relate to a system for thermalenergy storage, including an input, (e.g., electricity from a variablerenewable electricity (VRE) source), a container having sides, a roofand a lower platform, a plurality of vertically oriented thermal storageunits (TSUs), inside the container, the TSUs each including a pluralityof stacks of bricks and heaters attached thereto, each of the heatersbeing connected to the input electricity via switching circuitry, aninsulative layer interposed between the plurality of TSUs, the roof andat least one of the sides, a duct formed between the insulative layerand a boundary formed by the sides, an inner side of the roof and thelower platform of the container, a blower that blows relatively coolerfluid such as air or another gas (e.g. CO₂) along the flow path, anoutput (e.g., hot air at prescribed temperature to industrialapplication), a controller that controls and co-manages the energyreceived from the input and the hot air generated at the output based ona forecast associated with an ambient condition (e.g., season orweather) or a condition (e.g., output temperature, energy curve, etc.).The exterior and interior shapes of the container may be rectangular,cylindrical (in which case “sides” refers to the cylinder walls), orother shapes suitable to individual applications.

The terms air, fluid and gas are used interchangeably herein to refer toa fluid heat transfer medium of any suitable type, including varioustypes of gases (air, CO₂, oxygen and other gases, alone or incombination), and when one is mentioned, it should be understood thatthe others can equally well be used. Thus, for example, “air” can be anysuitable fluid or gas or combinations of fluids or gases.

Thermal energy storage (TES) systems according to the present designscan advantageously be integrated with or coupled to steam generators,including heat recovery steam generators (HRSGs) and once-through steamgenerators (OTSGs). The terms “steam generator”, “HRSG”, and “OTSG” areused interchangeably herein to refer to a heat exchanger that transfersheat from a first fluid into a second fluid, where the first fluid maybe air circulating from the TSU and the second fluid may be water (beingheated and/or boiled), oil, salt, air, CO₂, or another fluid. In suchimplementations, the heated first fluid is discharged from a TES unitand provided as input to the steam generator, which extracts heat fromthe discharged fluid to heat a second fluid, including producing steam,which heated second fluid may be used for any of a variety of purposes(e.g., to drive a turbine to produce shaft work or electricity). Afterpassing through a turbine, the second fluid still contains significantheat energy, which can be used for other processes. Thus, the TES systemmay drive a cogeneration process. The first fluid, upon exiting thesteam generator, can be fed back as input to the TES, thus capturingwaste heat to effectively preheat the input fluid. Waste heat fromanother process may also preheat input fluid to the TES.

According to another aspect, a dynamic insulation system include acontainer having sides, a roof and a lower platform, a plurality ofvertically oriented thermal storage units (TSUs) spaced apart from oneanother, an insulative layer interposed between the plurality of TSUs,the roof and at least one of the sides and floor, a duct formed betweenthe insulative layer and a boundary formed by the sides, an inner sideof the roof and the lower platform of the container, and a blower thatblows unheated air along the air flow path, upward from the platform toa highest portion of the upper portion, such that the air path is formedfrom the highest portion of the roof to the platform, and is heated bythe plurality of TSUs, and output from the TES apparatus. The unheatedair along the flow path forms an insulated layer and is preheated byabsorbing heat from the insulator.

II. Steam Cracking System and Applications

This Section II of the Summary relates to the newly added disclosure ofthis continuation-in-part application.

An inventive system and process includes a thermal energy storage system(TES) that captures and stores intermittent electrical energy byconverting it to high-temperature heat stored in a medium, anddischarges high temperature heat externally to a steam cracking system.Additional aspects may include a steam cracking application thatincludes the TES unit coupled to a steam cracking furnace system. Thesteam cracking process shown in FIGS. 7-15 is derived from an example,conventional, “fuel-fired” naphtha steam cracking plant. In some processintegrations, an electric steam cracker is assumed to fulfill the dutyof the “radiant zone” in a conventional process where preheatedfeedstock is subjected to rapid heating to cracking temperature beforebeing promptly cooled or quenched. In this integration, the heat batteryor TES is intended to fulfil the heat duty of the “convective zone” in aconventional process. The three process integrations are intended toshow increasing levels of replacement in the conventional steam crackingprocess. The electrified cases are sized to produce the same amount ofproduct cracked gas as the reference conventional case would, given acorresponding fuel input. Dilution steam is assumed to be available fromother processes around a petrochemical plant. The hot gas discharge fromthe heat battery or TES is designed to heat all desired components witha pinch temperature of at least 15° C. before being recirculated to theheat battery at a temperature between 125° C. and 200° C.

An aspect of the invention includes a preheat process. This aspect ofthe invention is the simplest process integration where hot gas from aTES, which is charged using electricity derived from renewable cleanenergy and/or from a grid, indirectly preheats some or all feedstockcomponents prior to their being passed into an electric cracker reactor.Another aspect of the invention includes a preheat and economizer. Thisnext level of integration is intended as a partial fulfillment of heatrecovery steam generation of a conventional process. Conventionally,steam cracking processes have been designed to recover the large amountof heat contained in flue gasses from the burners in the “radiant zone.”Because of this, steam cracking furnaces are often considered the‘heart’ of a petrochemical plant, as other petrochemical processes arebuilt around the cracker to utilize the waste heat it produces. Oftentimes, waste heat is used to generate steam for use in another processor for power generation. In this process integration, high pressureboiler feedwater which is ultimately used to quench the cracked productgas, is heated, in-line with the high temperature cracked gas streamexiting the radiant zone, to generate high pressure steam. Theintegrated system provides export steam in addition to quenched crackedgas.

Additional aspects may include a feedstock/dilution steam preheat,boiler feedwater economizer, and export steam superheat. This processintegration is configured to serve as an electrified, drop-inreplacement of a conventional steam cracker, either alone or along withother emission reduction technologies such that the TES integrationaddresses operational trade-offs that other emission reducingtechnologies may introduce. In the latter class of integrations, theintegration of the TES may enable the modified process to produce steamof the same quantity and conditions of the reference, conventionalprocess.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure and are incorporated in andconstitute a part of this specification. The drawings illustrate exampleimplementations of the present disclosure and, together with thedescription, serve to explain the principles of the present disclosure.

In the drawings, similar components and/or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label with a second label thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the second reference label.

FIGS. 1 to 6 appear in parent U.S. patent application Ser. No.17/668,333. FIGS. 7 to 17 include new disclosure of thiscontinuation-in-part application.

FIG. 1 illustrates a schematic diagram of the thermal energy storagesystem architecture according to the example implementations.

FIG. 2 illustrates a schematic diagram of a system according to theexample implementations.

FIG. 3 illustrates a schematic diagram of a storage-fired once-throughsteam generator (OTSG) according to the example implementations.

FIG. 4 illustrates an example view of a system being used as anintegrated cogeneration system according to the example implementations.

FIG. 5 illustrates dynamic insulation according to the exampleimplementations.

FIG. 6 provides an isometric view of the thermal storage unit withmultiple vents closures open, according to some implementations.

FIG. 7 illustrates a flow sheet of a conventional, “fuel-fired” naphthasteam cracking furnace.

FIG. 8 illustrates a simplified example system of a thermal storagesystem replacing heat from an efficiency improvement in the radiantsection.

FIG. 9 illustrates an implementation of a thermal energy storage system(TES) supporting the adoption of oxyfuel fired technology in a steamcracking furnace.

FIG. 10 illustrates an integration with an oxyfuel fired system with theonly change being the use of an electric booster heater to raise thetemperature of the TES to higher temperatures in a cracking furnace.

FIG. 11 illustrates a simplified example system of a thermal storagesystem that includes the addition of an electric booster heater toproduce higher temperature gas than the TES alone may be able to supplyin a steam cracking furnace.

FIG. 12 illustrates an abstracted schematic of a TES replacing all thepreheating and export steam heating of a steam cracking system that usesand electric cracker to perform the cracking reaction.

FIG. 12A illustrates a simplified block diagram of the system of FIG. 12showing the TES replacing all the preheating of a steam cracking systemthat uses and electric cracker to perform the cracking reaction.

FIG. 12B illustrates a simplified block diagram of the system of FIG. 12showing the TES replacing all the preheating and a portion of the exportsteam heating duty of a steam cracking system that uses and electriccracker to perform the cracking reaction.

FIG. 12C illustrates a simplified block diagram of the system of FIG. 12.

FIG. 13 illustrates an electric booster that may be used to furtherboost the temperature of the gas to higher temperatures than the thermalstorage system can provide in a steam cracking furnace.

FIG. 14 illustrates how the TES may supply high temperature gas attemperatures much higher than conventional flame temperatures used inthe radiant zone in a steam cracking furnace.

FIG. 15 illustrates a variation of a TES supplying all heat for thesteam cracking process with radiant tubing interacting directly with theTES.

FIG. 15A illustrates the integrated system of FIG. 15 in which exportsteam is provided to a thermal power cycle to generate electricity thatis directed back to the TES.

FIG. 16 illustrates a steam cracking system integrated with a thermalstorage system which supplies heat for feedstock preheating and steamgeneration for power generation to power an electrically heated cracker.

FIG. 17 illustrates a steam cracking system integrated with a thermalstorage system which supplies heat for feedstock preheating and crackingand steam generation for power generation.

DETAILED DESCRIPTION

Aspects of the example implementations, as disclosed herein, relate tosystems, methods, materials, compositions, articles, and improvementsfor a thermal energy storage system for power generation for variousindustrial applications.

I. Thermal Energy Storage System

This Section I of the Summary relates to the disclosure as it appears inU.S. Pat. No. 11,603,776, of which this application is acontinuation-in-part.

U.S. Pat. No. 11,603,776 relates to the field of thermal energy storageand utilization systems and addresses the above-noted problems. Athermal energy storage system is disclosed that stores electrical energyin the form of thermal energy in a charging mode and delivers the storedenergy in a discharging mode. The discharging can occur at the same timeas charging; i.e., the system may be heated by electrical energy at thesame time that it is providing a flow of convectively heated air. Thedischarged energy is in the form of hot air, hot fluids in general,steam, heated CO₂, heated supercritical CO₂, and/or electrical powergeneration, and can be supplied to various applications, includingindustrial uses. The disclosed implementations include efficientlyconstructed, long-service-life thermal energy storage systems havingmaterials, fabrication, physical shape, and other properties thatmitigate damage and deterioration from repeated temperature cycling.

Optionally, heating of the elements of the storage unit may beoptimized, so as to store a maximum amount of heat during the chargingcycle. Alternatively, heating of elements may be optimized to maximizeheating element life, by means including minimizing time at particularheater temperatures, and/or by adjusting peak charging rates and/or peakheating element temperatures. Still other alternatives may balance thesecompeting interests. Specific operations to achieve these optimizationsare discussed further below.

Example implementations employ efficient yet economical thermalinsulation. Specifically, a dynamic insulation design may be used eitherby itself or in combination with static primary thermal insulation. Thedisclosed dynamic insulation techniques provide a controlled flow of airinside the system to restrict dissipation of thermal energy to theoutside environment, which results in higher energy storage efficiency.

System Overview as Disclosed in U.S. Pat. No. 11,603,776

FIG. 1 is a block diagram of a system 1 that includes a thermal energystorage system 10, according to one implementation. In theimplementation shown, thermal energy storage system 10 is coupledbetween an input energy source 2 and a downstream energy-consumingprocess 22. For ease of reference, components on the input and outputsides of system 1 may be described as being “upstream” and “downstream”relative to system 10.

In the depicted implementation, thermal energy storage system 10 iscoupled to input energy source 2, which may include one or more sourcesof electrical energy. Source 2 may be renewable, such as photovoltaic(PV) cell or solar, wind, geothermal, etc. Source 2 may also be anothersource, such as nuclear, natural gas, coal, biomass, or other. Source 2may also include a combination of renewable and other sources. In thisimplementation, source 2 is provided to thermal energy storage system 10via infrastructure 4, which may include one or more electricalconductors, commutation equipment, etc. In some implementations,infrastructure 4 may include circuitry configured to transportelectricity over long distances; alternatively, in implementations inwhich input energy source 2 is located in the immediate vicinity ofthermal energy storage system 10, infrastructure 4 may be greatlysimplified. Ultimately, infrastructure 4 delivers energy to input 5 ofthermal energy storage system 10 in the form of electricity.

The electrical energy delivered by infrastructure 4 is input to thermalstorage structure 12 within system 10 through switchgear, protectiveapparatus and active switches controlled by control system 15. Thermalstorage structure 12 includes thermal storage 14, which in turn includesone more assemblages (e.g., 14A, 14B) of solid storage media (e.g., 13A,13B) configured to store thermal energy. These assemblages are variouslyreferred to throughout this disclosure as “stacks,” “arrays,” and thelike. These terms are intended to be generic and not connote anyparticular orientation in space, etc. In general, an array can includeany material that is suitable for storing thermal energy and can beoriented in any given orientation (e.g., vertically, horizontally,etc.). Likewise, the solid storage media within the assemblages mayvariously be referred to as thermal storage blocks, bricks, etc. Inimplementations with multiple arrays, the arrays may be thermallyisolated from one another and are separately controllable, meaning thatthey are capable of being charged or discharged independently from oneanother. This arrangement provides maximum flexibility, permittingmultiple arrays to be charged at the same time, multiple arrays to becharged at different times or at different rates, one array to bedischarged while the other array remains charged, etc.

Thermal storage 14 is configured to receive electrical energy as aninput. The received electrical energy may be provided to thermal storage14 via resistive heating elements that are heated by electrical energyand emit heat, primarily as electromagnetic radiation in the infraredand visible spectrum. During a charging mode of thermal storage 14, theelectrical energy is released as heat from the resistive heatingelements, transferred principally by radiation emitted both by theheating elements and by hotter solid storage media, and absorbed andstored in solid media within storage 14. When an array within thermalstorage 14 is in a discharging mode, the heat is discharged from thermalstorage structure 12 as output 20. As will be described, output 20 maytake various forms, including a fluid such as hot air. (References tothe use of “air” and “gases” within the present disclosure may beunderstood to refer more generally to a “fluid.”) The hot air may beprovided directly to a downstream energy consuming process 22 (e.g., anindustrial application), or it may be passed through a steam generator(not shown) to generate steam for process 22.

Additionally, thermal energy storage system 10 includes a control system15. Control system 15, in various implementations, is configured tocontrol thermal storage 14, including through setting operationalparameters (e.g., discharge rate), controlling fluid flows, controllingthe actuation of electromechanical or semiconductor electrical switchingdevices, etc. The interface 16 between control system 15 and thermalstorage structure 12 (and, in particular thermal storage 14) isindicated in FIG. 1 . Control system 15 may be implemented as acombination of hardware and software in various embodiments.

Control system 15 may also interface with various entities outsidethermal energy storage system 10. For example, control system 15 maycommunicate with input energy source 2 via an input communicationinterface 17B. For example, interface 17B may allow control system 15 toreceive information relating to energy generation conditions at inputenergy source 2. In the implementation in which input energy source 2 isa photovoltaic array, this information may include, for example, currentweather conditions at the site of source 2, as well as other informationavailable to any upstream control systems, sensors, etc. Interface 17Bmay also be used to send information to components or equipmentassociated with source 2.

Similarly, control system 15 may communicate with infrastructure 4 viaan infrastructure communication interface 17A. In a manner similar tothat explained above, interface 17A may be used to provideinfrastructure information to control system 15, such as current orforecast VRE availability, grid demand, infrastructure conditions,maintenance, emergency information, etc. Conversely, communicationinterface 17A may also be used by control system 15 to send informationto components or equipment within infrastructure 4. For example, theinformation may include control signals transmitted from the controlsystem 15, that controls valves or other structures in the thermalstorage structure 12 to move between an open position and a closedposition, or to control electrical or electronic switches connected toheaters in the thermal storage 14. Control system 15 uses informationfrom communication interface 17A in determining control actions, andcontrol actions may adjust closing or firing of switches in a manner tooptimize the use of currently available electric power and maintain thevoltage and current flows within infrastructure 4 within chosen limits.

Control system 15 may also communicate downstream using interfaces 18Aand/or 18B. Interface 18A may be used to communicate information to anyoutput transmission structure (e.g., a steam transmission line), whileinterface 18B may be used to communicate with downstream process 22. Forexample, information provided over interfaces 18A and 18B may includetemperature, industrial application demand, current or future expectedconditions of the output or industrial applications, etc. Control system15 may control the input, heat storage, and output of thermal storagestructure based on a variety of information. As with interfaces 17A and17B, communication over interfaces 18A and 18B may be bidirectional—forexample, system 10 may indicate available capacity to downstream process22. Still further, control system 15 may also communicate with any otherrelevant data sources (indicated by reference numeral 21 in FIG. 1 ) viaadditional communication interface 19. Additional data sources 21 arebroadly intended to encompass any other data source not maintained byeither the upstream or downstream sites. For example, sources 21 mightinclude third-party forecast information, data stored in a cloud datasystem, etc.

Thermal energy storage system 10 is configured to efficiently storethermal energy generated from input energy source 2 and deliver outputenergy in various forms to a downstream process 22. In variousimplementations, input energy source 2 may be from renewable energy anddownstream process 22 may be an industrial application that requires aninput such as steam or hot air. Through various techniques, includingarrays of thermal storage blocks that use radiant heat transfer toefficiently storage energy and a lead-lag discharge paradigm that leadsto desirable thermal properties such as the reduction of temperaturenonuniformities within thermal storage 14, system 10 may advantageouslyprovide a continuous (or near-continuous) flow of output energy based onan intermittently available source. The use of such a system has thepotential to reduce the reliance of industrial applications on fossilfuels.

FIG. 2 provides a schematic view of one implementation of a system 200for storing thermal energy, and further illustrates components andconcepts just described with respect to FIG. 1 . As shown, one or moreenergy sources 201 provide input electricity. For example, and as notedabove, renewable sources such as wind energy from wind turbines 201 a,solar energy from photovoltaic cells 201 b, or other energy sources mayprovide electricity that is variable in availability or price becausethe conditions for generating the electricity are varied. For example,in the case of wind turbine 201 a, the strength, duration and varianceof the wind, as well as other weather conditions causes the amount ofenergy that is produced to vary over time. Similarly, the amount ofenergy generated by photovoltaic cells 201 b also varies over time,depending on factors such as time of day, length of day due to the timeof year, level of cloud cover due to weather conditions, temperature,other ambient conditions, etc. Further, the input electricity may bereceived from the existing power grid 201 c, which may in turn varybased on factors such as pricing, customer demand, maintenance, andemergency requirements.

The electricity generated by source 201 is provided to the thermalstorage structure within the thermal energy storage system. In FIG. 2 ,the passage of electricity into the thermal storage structure isrepresented by wall 203. The input electrical energy is converted toheat within thermal storage 205 via resistive heating elements 207controlled by switches (not shown). Heating elements 207 provide heat tosolid storage media 209. Thermal storage components (sometimes called“bricks”) within thermal storage 205 are arranged to form embeddedradiative chambers. FIG. 2 illustrates that multiple thermal storagearrays 209 may be present within system 200. These arrays may bethermally isolated from one another and may be separately controllable.FIG. 2 is merely intended to provide a conceptual representation of howthermal storage 205 might be implemented—one such implementation might,for example, include only two arrays, or might include six arrays, orten arrays, or more.

In the depicted implementation, a blower 213 drives air or other fluidto thermal storage 205 such that the air is eventually received at alower portion of each of the arrays 209. The air flows upward throughthe channels and chambers formed by bricks in each of the arrays 209,with flow controlled by louvers. By the release of heat energy from theresistive heating elements 207, heat is radiatively transferred toarrays 209 of bricks during a charging mode. Relatively hotter bricksurfaces reradiate absorbed energy (which may be referred to as aradiative “echo”) and participate in heating cooler surfaces. During adischarging mode, the heat stored in arrays 209 is output, as indicatedat 215.

Once the heat has been output in the form of a fluid such as hot air,the fluid may be provided for one or more downstream applications. Forexample, hot air may be used directly in an industrial process that isconfigured to receive the hot air, as shown at 217. Further, hot air maybe provided as a stream 219 to a heat exchanger 218 of a steam generator222, and thereby heats a pressurized fluid such as air, water, CO₂ orother gas. In the example shown, as the hot air stream 219 passes over aline 221 that provides the water from the pump 223 as an input, thewater is heated and steam is generated as an output 225, which may beprovided to an industrial application as shown at 227.

A thermal storage structure such as that depicted in FIGS. 1-2 may alsoinclude output equipment configured to produce steam for use in adownstream application. FIG. 3 , for example, depicts a block diagram ofan implementation of a thermal storage structure 300 that includes astorage-fired once-through steam generator (OTSG). An OTSG is a type ofheat recovery stream generator (HRSG), which is a heat exchanger thataccepts hot air from a storage unit, returns cooler air, and heats anexternal process fluid. The depicted OTSG is configured to use thermalenergy stored in structure 300 to generate steam at output 311.

As has been described, thermal storage structure 300 includes outerstructure 301 such walls, a roof, as well as thermal storage 303 in afirst section of the structure. The OTSG is located in a second sectionof the structure, which is separated from the first section by thermalbarrier 325. During a charging mode, thermal energy is stored in thermalstorage 303. During a discharging mode, the thermal energy stored inthermal storage 303 receives a fluid flow (e.g., air) by way of a blower305. These fluid flows may be generated from fluid entering structure300 via an inlet valve 319 and include a first fluid flow 312A (whichmay be directed to a first stack within thermal storage 303) and asecond fluid flow 312B (which may be directed to a second stack withinthermal storage 303).

As the air or other fluid directed by blower 305 flows through thethermal storage 303 from the lower portion to the upper portion, it isheated and is eventually output at the upper portion of thermal storage303. The heated air, which may be mixed at some times with a bypassfluid flow 312C that has not passed through thermal storage 302, ispassed over a conduit 309 through which flows water, or another fluidpumped by the water pump 307. As the hot air heats up the water in theconduit, steam is generated at 311. The cooled air that has crossed theconduit (and transferred heat to the water flowing through it) is thenfed back into the brick heat storage 303 by blower 305. As explainedbelow, the control system can be configured to control attributes of thesteam, including steam quality, or fraction of the steam in the vaporphase, and flow rate.

As shown in FIG. 3 , an OTSG does not include a recirculating drumboiler. Properties of steam produced by an OTSG are generally moredifficult to control than those of steam produced by a more traditionalHRSG with a drum, or reservoir. The steam drum in such an HRSG acts as aphase separator for the steam being produced in one or more heated tubesrecirculating the water; water collects at the bottom of the reservoirwhile the steam rises to the top. Saturated steam (having a steamquality of 100%) can be collected from the top of the drum and can berun through an additional heated tube structure to superheat it andfurther assure high steam quality. Drum-type HRSGs are widely used forpower plants and other applications in which the water circulatingthrough the steam generator is highly purified and stays clean in aclosed system. For applications in which the water has significantmineral content, however, mineral deposits form in the drum and tubesand tend to clog the system, making a recirculating drum designinfeasible.

For applications using water with a higher mineral content, an OTSG maybe a better option. One such application is oil extraction, in whichfeed water for a steam generator may be reclaimed from a water/oilmixture produced by a well. Even after filtering and softening, suchwater may have condensed solid concentrations on the order of 10,000 ppmor higher. The lack of recirculation in an OTSG enables operation in amode to reduce mineral deposit formation; however, an OTSG needs to beoperated carefully in some implementations to avoid mineral deposits inthe OTSG water conduit. For example, having some fraction of waterdroplets present in the steam as it travels through the OTSG conduit maybe required to prevent mineral deposits by retaining the minerals insolution in the water droplets. This consideration suggests that thesteam quality (vapor fraction) of steam within the conduit must bemaintained below a specified level. On the other hand, a high steamquality at the output of the OTSG may be important for the processemploying the steam. Therefore, it is advantageous for a steam generatorpowered by VRE through TES to maintain close tolerances on outlet steamquality. There is a sensitive interplay among variables such as inputwater temperature, input water flow rate and heat input, which must bemanaged to achieve a specified steam quality of output steam whileavoiding damage to the OTSG.

Implementations of the thermal energy storage system disclosed hereinprovide a controlled and specified source of heat to an OTSG. Thecontrolled temperature and flow rate available from the thermal energystorage system allows effective feed-forward and feedback control of thesteam quality of the OTSG output. In one implementation, feed-forwardcontrol includes using a target steam delivery rate and steam qualityvalue, along with measured water temperature at the input to the waterconduit of the OTSG, to determine a heat delivery rate required by thethermal energy storage system for achieving the target values. In thisimplementation, the control system can provide a control signal tocommand the thermal storage structure to deliver the flowing gas acrossthe OTSG at the determined rate. In one implementation, a thermal energystorage system integrated with an OTSG includes instrumentation formeasurement of the input water temperature to the OTSG.

In one implementation, feedback control includes measuring a steamquality value for the steam produced at the outlet of the OTSG, and acontroller using that value to adjust the operation of the system toreturn the steam quality to a desired value. Obtaining the outlet steamquality value may include separating the steam into its liquid and vaporphases and independently monitoring the heat of the phases to determinethe vapor phase fraction. Alternatively, obtaining the outlet steamquality value may include measuring the pressure and velocity of theoutlet steam flow and the pressure and velocity of the inlet water flow,and using the relationship between values to calculate an approximationof the steam quality. Based on the steam quality value, a flow rate ofthe outlet fluid delivered by the thermal storage to the OTSG may beadjusted to achieve or maintain the target steam quality. In oneimplementation, the flow rate of the outlet fluid is adjusted byproviding a feedback signal to a controllable element of the thermalstorage system. The controllable element may be an element used inmoving fluid through the storage medium, such as a blower or other fluidmoving device, a louver, or a valve.

The steam quality measurement of the outlet taken in real time may beused as feedback by the control system to determine the desired rate ofheat delivery to the OTSG. To accomplish this, an implementation of athermal energy storage system integrated with an OTSG may includeinstruments to measure inlet water velocity and outlet steam flowvelocity, and, optionally, a separator along with instruments forproviding separate measurements of the liquid and vapor heat values. Insome implementations, the tubing in an OTSG is arranged such that thetubing closest to the water inlet is positioned in the lowesttemperature portion of the airflow, and that the tubing closest to thesteam exit is positioned in the highest temperature portion of theairflow. In some implementations of the present innovations, the OTSGmay instead be configured such that the highest steam quality tubes(closest to the steam outlet) are positioned at some point midwaythrough the tubing arrangement, so as to enable higher inlet fluidtemperatures from the TSU to the OTSG while mitigating scale formationwithin the tubes and overheating of the tubes, while maintaining propersteam quality. The specified flow parameters of the heated fluidproduced by thermal energy storage systems as disclosed herein may insome implementations allow precise modeling of heat transfer as afunction of position along the conduit. Such modeling may allow specificdesign of conduit geometries to achieve a specified steam qualityprofile along the conduit.

As shown in FIG. 4 , the output of the thermal energy storage system maybe used for an integrated cogeneration system 400. As previouslyexplained, an energy source 401 provides electrical energy that isstored as heat in the heat storage 403 of the TSU. During discharge, theheated air is output at 405. As shown in FIG. 4 , lines containing afluid, in this case water, are pumped into a drum 406 of an HRSG 409 viaa preheating section of tubing 422. In this implementation, HRSG 409 isa recirculating drum type steam generator, including a drum or boiler406 and a recirculating evaporator section 408. The output steam passesthrough line 407 to a superheater coil, and is then provided to aturbine at 415, which generates electricity at 417. As an output, theremaining steam 421 may be expelled to be used as a heat source for aprocess or condensed at 419 and optionally passed through to adeaeration unit 413 and delivered to pump 411 in order to performsubsequent steam generation.

Certain industrial applications may be particularly well-suited forcogeneration. For example, some applications use higher temperature heatin a first system, such as to convert the heat to mechanical motion asin the case of a turbine, and lower-temperature heat discharged by thefirst system for a second purpose, in a cascading manner; or an inversetemperature cascade may be employed. One example involves a steamgenerator that makes high-pressure steam to drive a steam turbine thatextracts energy from the steam, and low-pressure steam that is used in aprocess, such as an ethanol refinery, to drive distillation and electricpower to run pumps. Still another example involves a thermal energystorage system in which hot gas is output to a turbine, and the heat ofthe turbine outlet gas is used to preheat inlet water to a boiler forprocessing heat in another steam generator (e.g., for use in an oilfieldindustrial application). In one application, cogeneration involves theuse of hot gas at e.g., 840° C. to power or co-power hydrogenelectrolysis, and the lower temperature output gas of the hydrogenelectrolyzer, which may be at about 640° C., is delivered alone or incombination with higher-temperature heat from a TSU to a steam generatoror a turbine for a second use. In another application, cogenerationinvolves the supply of heated gas at a first temperature e.g., 640° C.to enable the operation of a fuel cell, and the waste heat from the fuelcell which may be above 800° C. is delivered to a steam generator or aturbine for a second use, either alone or in combination with other heatsupplied from a TSU.

A cogeneration system may include a heat exchange apparatus thatreceives the discharged output of the thermal storage unit and generatessteam. Alternately, the system may heat another fluid such assupercritical carbon dioxide by circulating high-temperature air fromthe system through a series of pipes carrying a fluid, such as water orCO₂, (which transfers heat from the high-temperature air to the pipesand the fluid), and then recirculating the cooled air back as an inputto the thermal storage structure. This heat exchange apparatus is anHRSG, and in one implementation is integrated into a section of thehousing that is separated from the thermal storage.

The HRSG may be physically contained within the thermal storagestructure or may be packaged in a separate structure with ductsconveying air to and from the HRSG. The HRSG can include a conduit atleast partially disposed within the second section of the housing. Inone implementation, the conduit can be made of thermally conductivematerial and be arranged so that fluid flows in a “once-through”configuration in a sequence of tubes, entering as lower-temperaturefluid and exiting as higher temperature, possibly partially evaporated,two-phase flow. As noted above, once-through flow is beneficial, forexample, in processing feedwater with substantial dissolved mineralcontaminants to prevent accumulation and precipitation within theconduits.

In an OTSG implementation, a first end of the conduit can be fluidicallycoupled to a water source. The system may provide for inflow of thefluids from the water source into a first end of the conduit and enableoutflow of the received fluid or steam from a second end of the conduit.The system can include one or more pumps configured to facilitate inflowand outflow of the fluid through the conduit. The system can include aset of valves configured to facilitate controlled outflow of steam fromthe second end of the conduit to a second location for one or moreindustrial applications or electrical power generation. As shown in FIG.6 , an HRSG may also be organized as a recirculating drum-type boilerwith an economizer and optional superheater, for the delivery ofsaturated or superheated steam.

The output of the steam generator may be provided for one or moreindustrial uses. For example, steam may be provided to a turbinegenerator that outputs electricity for use as retail local power. Thecontrol system may receive information associated with local powerdemands, and determine the amount of steam to provide to the turbine, sothat local power demands can be met.

In addition to the generation of electricity, the output of the thermalstorage structure may be used for industrial applications as explainedbelow. Some of these applications may include, but are not limited to,electrolyzers, fuel cells, gas generation units such as hydrogen, carboncapture, manufacture of materials such as cement, calciningapplications, as well as others. More details of these industrialapplications are provided below.

Dynamic Insulation

It is generally beneficial for a thermal storage structure to minimizeits total energy losses via effective insulation, and to minimize itscost of insulation. Some insulation materials are tolerant of highertemperatures than others. Higher-temperature tolerant materials tend tobe more costly.

FIG. 5 provides a schematic section illustration 500 of animplementation of dynamic insulation. The outer container includes roof501, walls 503, 507 and a foundation 509. Within the outer container, alayer of insulation 511 is provided between the outer container andcolumns of bricks in stack 513, the columns being represented as 513 a,513 b, 513 c, 513 d and 513 e. The heated fluid that is discharged fromthe upper portion of the columns of bricks 513 a, 513 b, 513 c, 513 dand 513 e exits by way of an output 515, which is connected to a duct517. Duct 517 provides the heated fluid as an input to a steam generator519. Once the heated fluid has passed through steam generator 519, someof its heat is transferred to the water in the steam generator and thestream of fluid is cooler than when exiting the steam generator.Further, the heated fluid may be used directly in an industrial process520 that is configured to receive the heated fluid, as shown at 518.Cooler recycled fluid exits a bottom portion 521 of the steam generator519. An air blower 523 receives the cooler fluid, and provides thecooler fluid, via a passage 525 defined between the walls 503 andinsulation 527 positioned adjacent the stack 513, through an upper airpassage 529 defined between the insulation 511 and the roof 501, downthrough side passages 531 defined on one or more sides of the stack 513and the insulation 511, and thence down to a passage 533 directly belowthe stack 513.

The air in passages 525, 529, 531 and 533 acts as an insulating layerbetween (a) the insulations 511 and 527 surrounding the stack 513, and(b) the roof 501, walls 503, 507 and foundation 509. Thus, heat from thestack 513 is prevented from overheating the roof 501, walls 503, 507 andfoundation 509. At the same time, the air flowing through those passages525, 529, 531 and 533 carries by convection heat that may penetrate theinsulations 511 and/or 517 into air flow passages 535 of the stack 513,thus preheating the air, which is then heated by passage through the airflow passages 535.

The columns of bricks 513 a, 513 b, 513 c, 513 d and 513 e and the airpassages 535 are shown schematically in FIG. 5 . The physical structureof the stacks and air flow passages therethrough in embodimentsdescribed herein is more complex, leading to advantages.

In some implementations, to reduce or minimize the total energy loss,the layer of insulation 511 is a high-temperature primary insulationthat surrounds the columns 513 a, 513 b, 513 c, 513 d and 513 e withinthe housing. Outer layers of lower-cost insulation may also be provided.The primary insulation may be made of thermally insulating materialsselected from any combination of refractory bricks, alumina fiber,ceramic fiber, and fiberglass or any other material that might beapparent to a person of ordinary skill in the art. The amount ofinsulation required to achieve low losses may be large, given the hightemperature differences between the storage media and the environment.To reduce energy losses and insulation costs, conduits are arranged todirect returning, cooler fluid from the HRSG along the outside of aprimary insulation layer before it flows into the storage core forreheating.

The cooler plenum, including passages 525, 529, 531 and 533, isinsulated from the outside environment, but total temperaturedifferences between the cooler plenum and the outside environment arereduced, which in turn reduces thermal losses. This technique, known as“dynamic insulation,” uses the cooler returning fluid, as describedabove, to recapture heat which passes through the primary insulation,preheating the cooler air before it flows into the stacks of the storageunit. This approach further serves to maintain design temperatureswithin the foundation and supports of the thermal storage structure.Requirements for foundation cooling in existing designs (e.g., formolten salt) involve expensive dedicated blowers andgenerators—requirements avoided by implementations according to thepresent teaching.

The materials of construction and the ground below the storage unit maynot be able to tolerate high temperatures, and in the present systemactive cooling—aided by the unassisted flowing heat exchange fluid inthe case of power failure—can maintain temperatures within designlimits.

A portion of the fluid returning from the HRSG may be directed throughconduits such as element 521 located within the supports and foundationelements, cooling them and delivering the captured heat back to theinput of the storage unit stacks as preheated fluid. The dynamicinsulation may be provided by arranging the bricks 513 a, 513 b, 513 c,513 d and 513 e within the housing so that the bricks 513 a, 513 b, 513c, 513 d and 513 e are not in contact with the outer surface 501, 503,507 of the housing, and are thus thermally isolated from the housing bythe primary insulation formed by the layer of cool fluid. The bricks 513a, 513 b, 513 c, 513 d and 513 e may be positioned at an elevated heightfrom the bottom of the housing, using a platform made of thermallyinsulating material.

During unit operation, a controlled flow of relatively cool fluid isprovided by the fluid blowing units 523, to a region (including passages525, 529, 531 and 533) between the housing and the primary insulation(which may be located on an interior or exterior of an inner enclosurefor one or more thermal storage assemblages), to create the dynamicthermal insulation between the housing and the bricks, which restrictsthe dissipation of thermal energy being generated by the heatingelements and/or stored by the bricks into the outside environment or thehousing, and preheats the fluid. As a result, the controlled flow ofcold fluid by the fluid blowing units of the system may facilitatecontrolled transfer of thermal energy from the bricks to the conduit,and also facilitates dynamic thermal insulation, thereby making thesystem efficient and economical.

In another example implementation, the buoyancy of fluid can enable anunassisted flow of the cold fluid around the bricks between the housingand the primary insulator 511 such that the cold fluid may providedynamic insulation passively, even when the fluid blowing units 523 failto operate in case of power or mechanical failure, thereby maintainingthe temperature of the system within predefined safety limits, toachieve intrinsic safety. The opening of vents, ports, or louvres (notshown) may establish passive buoyancy-driven flow to maintain such flow,including cooling for supports and foundation cooling, during such poweroutages or unit failures, without the need for active equipment.

In the above-described fluid flow, the fluid flows to an upper portionof the unit, down the walls and into the inlet of the stacking,depending on the overall surface area to volume ratio, which is in turndependent on the overall unit size, the flow path of the dynamicinsulation may be changed. For example, in the case of smaller unitsthat have greater surface area as compared with the volume, the amountof fluid flowing through the stack relative to the area may utilize aflow pattern that includes a series of serpentine channels, such thatthe fluid flows on the outside, moves down the wall, up the wall, anddown the wall again before flowing into the inlet. Other channelizationpatterns may also be used.

Additionally, the pressure difference between the return fluid in theinsulation layer and the fluid in the stacks may be maintained such thatthe dynamic insulation layer has a substantially higher pressure thanthe pressure in the stacks themselves. Thus, if there is a leak betweenthe stacks and the insulation, the return fluid at the higher pressuremay be forced into the leak or the cracks, rather than the fluid withinthe stacks leaking out into the dynamic insulation layer. Accordingly,in the event of a leak in the stacks, the very hot fluid of the stacksmay not escape outside of the unit, but instead the return fluid maypush into the stacks, until the pressure between the dynamic insulationlayer in the stacks equalizes. Pressure sensors may be located on eitherside of the blower that provide relative and absolute pressureinformation. With such a configuration, a pressure drop within thesystem may be detected, which can be used to locate the leak.

Earlier systems that store high temperature sensible heat in rocks andmolten salts have required continuous active means of coolingfoundations, and in some implementations continuous active means ofheating system elements to prevent damage to the storage system; thus,continuous active power and backup power supply systems are required. Asystem as described herein does not require an external energy supply tomaintain the safety of the unit. Instead, as described below, thepresent disclosure provides a thermal storage structure that providesfor thermally induced flows that passively cools key elements whenequipment, power, or water fails. This also reduces the need for fans orother cooling elements inside the thermal storage structure.

Forecast-Based System Control

As noted above, forecast information such as weather predictions may beused by a control system to reduce wear and degradation of systemcomponents. Another goal of forecast-based control is to ensure adequatethermal energy production from the thermal energy storage system to theload or application system. Actions that may be taken in view offorecast information include, for example, adjustments to operatingparameters of the thermal energy storage system itself, adjustments toan amount of input energy coming into the thermal energy storage system,and actions or adjustments associated with a load system receiving anoutput of the thermal energy storage system.

Weather forecasting information can come from one or more of multiplesources. One source is a weather station at a site located with thegeneration of electrical energy, such as a solar array or photovoltaicarray, or wind turbines. The weather station may be integrated with apower generation facility, and may be operationally used for controldecisions of that facility, such as for detection of icing on windturbines. Another source is weather information from sources covering awider area, such as radar or other weather stations, which may be fedinto databases accessible by the control system of the thermal energystorage system. Weather information covering a broader geography may beadvantageous in providing more advanced notice of changes in condition,as compared to the point source information from a weather stationlocated at the power source. Still another possible source of weatherinformation is virtual or simulated weather forecast information. Ingeneral, machine learning methods can be used to train the system,taking into account such data and modifying behavior of the system.

As an example, historical information associated with a power curve ofan energy source may be used as a predictive tool, taking into accountactual conditions, to provide forecasting of power availability andadjust control of the thermal energy storage system, both as to theamount of energy available to charge the units and the amount ofdischarge heat output available. For example, the power curveinformation may be matched with actual data to show that when the poweroutput of a photovoltaic array is decreasing, it may be indicative of acloud passing over one or more parts of the array, or cloudy weathergenerally over the region associated with the array.

Forecast-related information is used to improve the storage andgeneration of heat at the thermal energy storage system in view ofchanging conditions. For example, a forecast may assist in determiningthe amount of heat that must be stored and the rate at which heat mustbe discharged in order to provide a desired output to an industrialapplication—for instance, in the case of providing heat to a steamgenerator, to ensure a consistent quality and amount of steam, and toensure that the steam generator does not have to shut down. Thecontroller may adjust the current and future output of heat in responseto current or forecast reductions in the availability of chargingelectricity, so as to ensure across a period of future time that thestate of charge of the storage unit does not reduce so that heat outputmust be stopped. By adjusting the continuous operation of a steamgenerator to a lower rate in response to a forecasted reduction ofavailable input energy, the unit may operate continuously. The avoidanceof shutdowns and later restarts is an advantageous feature: shuttingdown and restarting a steam generator is a time-consuming process thatis costly and wasteful of energy, and potentially exposes personnel andindustrial facilities to safety risks.

The forecast, in some cases, may be indicative of an expected lowerelectricity input or some other change in electricity input pattern tothe thermal energy storage system. Accordingly, the control system maydetermine, based on the input forecast information, that the amount ofenergy that would be required by the thermal energy storage system togenerate the heat necessary to meet the demands of the steam generatoror other industrial application is lower than the amount of energyexpected to be available. In one implementation, making thisdetermination involves considering any adjustments to operation of thethermal energy storage system that may increase the amount of heat itcan produce. For example, one adjustment that may increase an amount ofheat produced by the system is to run the heating elements in a thermalstorage assemblage at a higher power than usual during periods of inputsupply availability, in order to obtain a higher temperature of theassemblage and greater amount of thermal energy stored. Such“overcharging” or “supercharging” of an assemblage, as discussed furtherbelow, may in some implementations allow sufficient output heat to beproduced through a period of lowered input energy supply. Overchargingmay increase stresses on the thermal storage medium and heater elementsof the system, thus increasing the need for maintenance and the risk ofequipment failure.

As an alternative to operational adjustments for the thermal energystorage system, or in embodiments for which such adjustments are notexpected to make up for a forecasted shortfall of input energy, actionon either the source side or the load side of the thermal energy storagesystem may be initiated by the control system. On the input side, forexample, the forecast difference between predicted and needed inputpower may be used to provide a determination, or decision-support, withrespect to sourcing input electrical energy from other sources during anupcoming time period, to provide the forecasted difference. For example,if the forecasting system determines that the amount of electricalenergy to be provided from a photovoltaic array will be 70% of theexpected amount needed over a given period of time, e.g., due to aforecast of cloudy weather, the control system may effectuate connectionto an alternative input source of electrical energy, such as windturbine, natural gas or other source, such that the thermal energystorage system receives 100% of the expected amount of energy. In animplementation of a thermal energy storage system having an electricalgrid connection available as an alternate input power source, thecontrol system may effectuate connection to the grid in response to aforecast of an input power shortfall.

In a particular implementation, forecast data may be used to determinedesired output rates for a certain number of hours or days ahead,presenting to an operator signals and information relating to expectedoperational adjustments to achieve those output rates, and providing theoperator with a mechanism to implement the output rates as determined bythe system, or alternatively to modify or override those output rates.This may be as simple as a “click to accept” feedback option provided tothe operator, a dead-man's switch that automatically implements thedetermined output rates unless overridden, and/or more detailed optionsof control parameters for the system.

II. Heat Transport in TSU: Bricks and Heating Elements

A. Problems Solved by One or More Disclosed Embodiments

Traditional approaches to the formation of energy storage cells may havevarious problems and disadvantages. For example, traditional approachesmay not provide for uniform heating of the thermal energy storage cells.Instead, they may use structures that create uneven heating, such as hotspots and cold spots. Non-uniform heating may reduce the efficiency ofan energy storage system, lead to earlier equipment failure, causesafety problems, etc. Further, traditional approaches may suffer fromwear and tear on thermal energy storage cells. For example, stressessuch as mechanical and thermal stress may cause deterioration ofperformance, as well as destabilization of the material, such ascracking of the bricks.

B. Example Solutions Disclosed Herein

In some implementations, thermal storage blocks (e.g., bricks) havevarious features that facilitate more even distribution. As one example,blocks may be formed and positioned to define fluid flow pathways withchambers that are open to heating elements to receive radiative energy.Therefore, a given fluid flow pathway (e.g., oriented vertically fromthe top to bottom of a stack) may include two types of openings:radiation chambers that are open to a channel for a heating element andfluid flow openings (e.g., fluid flow slots) that are not open to thechannel. The radiation chambers may receive infrared radiation fromheater elements, which, in conjunction with conductive heating by theheater elements may provide more uniform heating of an assemblage ofthermal storage blocks, relative to traditional implementations. Thefluid flow openings may receive a small amount of radiative energyindirectly via the chambers, but are not directly open to the heatingelement. The stack of bricks may be used alone or in combination withother stacks of bricks to form the thermal storage unit, and one or morethermal storage units may be used together in the thermal energy storagesystem. As the fluid blower circulates the fluid through the structureduring charge and discharge as explained above, a thermocline may beformed in a substantially vertical direction. Further, the fluidmovement system may direct relatively cooler fluid for insulativepurposes, e.g., along the insulated walls and roof of the structure.Finally, a venting system may allow for controlled cooling formaintenance or in the event of power loss, water loss, blower failure,etc., which may advantageously improve safety relative to traditionaltechniques.

Designs according to the present disclosure combine several keyinnovations, which together address these challenges and enable acost-effective, safe, reliable high-temperature thermal energy storagesystem to be built and operated. A carefully structured solid mediasystem according to the present teaching incorporates structured airflowpassages which accomplish effective thermocline discharge; repeatedmixing chambers along the direction of air flow which mitigate thethermal effects of any localized air channel blockages ornonuniformities; effective shielding of thermal radiation frompropagating in the vertical direction; and a radiation chamber structurewhich uniformly and rapidly heats brick material with high heater powerloading, low and uniform exposed surface temperature, and long-distanceheat transfer within the storage media array via multi-step thermalradiation.

Innovative structures according to the present disclosure may comprisean array of bricks that form chambers. The bricks have structured airpassages, such that in the vertical direction air flows upwards in asuccession of open chambers and small air passages. In some embodiments,the array of bricks with internal air passages is organized in astructure such that the outer surface of each brick within the TSU coreforms a wall of a chamber in which it is exposed to radiation from otherbrick surfaces, as well as radiation originating from an electricalheater.

The chamber structure is created by alternating brick materials into acheckerboard-type pattern, in which each brick is surrounded on allsides by open chambers, and each open chamber has adjacent bricks as itswalls. In addition, horizontal parallel passages are provided that passthrough multiple chambers. Electrical heating elements that extendhorizontally through the array are installed in these passages. Anindividual heating element it may be exposed along its length to theinterior spaces of multiple chambers. Each brick within such acheckerboard structure is exposed to open chambers on all sides.Accordingly, during charging, radiant energy from multiple heatingelements heats all outer surfaces of each brick, contributing to therapid and even heating of the brick, and reducing reliance on conductiveheat transfer within the brick by limiting the internal dimensions ofthe brick.

The radiation chamber structure provides a key advance in the design andproduction of effective thermal energy storage systems that are chargedby electrical energy. The large surface area, which is radiativelyexposed to heaters, causes the average temperature of the large surfaceto determine the radiation balance and thus the surface temperature ofthe heater. This intrinsic uniformity enables a high wattage per unitarea of heater without the potential of localized overheating. Andexposed brick surfaces are larger per unit of mass than in priorsystems, meaning that incoming wattage per unit area is correspondinglysmaller, and consequently thermal stresses due to brick internaltemperature differences are lower. And critically, re-radiation ofenergy—radiation by hotter brick surfaces that is absorbed by coolerbrick surfaces—reduces by orders of magnitude the variations in surfacetemperature, and consequently reduces thermal stresses in brickmaterials exposed to radiant heat. Thus, the radiation chamber designeffectively enables heat to be delivered relatively uniformly to a largehorizontally oriented surface area and enables high wattage per unitarea of heater with relatively low wattage per unit area of brick.

Note that while this configuration is described in terms of “horizontal”and “vertical”, these are not absolute degree or angle restrictions.Advantageous factors include maintaining a thermocline and providing forfluid flow through the stack in a direction that results in convectiveheat transfer, exiting the stack at a relatively hotter portion of thethermocline. An additional advantageous factor that may be incorporatedis to position the stack in a manner that encourages buoyant, hot air torise through the stack and exit at the hot end of the thermocline; inthis case, a stack in which the hot end of the thermocline is at ahigher elevation than the cold end of the thermocline is effective, anda vertical thermocline maximizes that effectiveness.

An important advantage of this design is that uniformity of heatingelement temperature is strongly improved in designs according to thepresent disclosure. Any variations in brick heat conductivity, or anycracks forming in a brick that result in changed heat conductivity, arestrongly mitigated by radiation heat transfer away from the locationwith reduced conductivity. That is, a region reaching a highertemperature than nearby regions due to reduced effectiveness of internalconduction will be out of radiation balance with nearby surfaces, andwill as a result be rapidly cooled by radiation to a temperaturerelatively close to that of surrounding surfaces. As a result, boththermal stresses within solid media, and localized peak heatertemperatures, are reduced by a large factor compared to previousteachings.

The system may include one or more air blowing units including anycombination of fans and, blowers, and configured at predefined positionsin the housing to facilitate the controlled flow of air between acombination of the first section, the second section, and the outsideenvironment. The first section may be isolated from the second sectionby a thermal barrier. The air blowing units may facilitate the flow ofair through at least one of the channels of the bricks from the bottomend of the cells to the upper end of the cells in the first section atthe predefined flow rate, and then into the second section, such thatthe air passing through the bricks and/or heating elements of the cellsat the predefined flow rate may be heated to a second predefinedtemperature, and may absorb and transfer the thermal energy emitted bythe heating elements and/or stored by the bricks within the secondsection. The air may flow from the second section across a steamgenerator or other heat exchanger containing one or more conduits, whichcarry a fluid, and which, upon receiving the thermal energy from the airhaving the second predefined temperature, may heat the fluid flowingthrough the conduit to a higher temperature or may convert the fluidinto steam. Further, the system may facilitate outflow of the generatedsteam from the second end of the conduit, to a predefined location forone or more industrial applications. The second predefined temperatureof the air may be based on the material being used in conduit, and therequired temperature and pressure of the steam. In anotherimplementation, the air leaving the second section may be deliveredexternally to an industrial process.

Additionally, the example implementations described herein disclose aresistive heating element. The resistive heating element may include aresistive wire. The resistive wire may have a cross-section that issubstantially round, elongated, flat, or otherwise shaped to admit asheat the energy received from the input of electrical energy.

Passive Cooling

FIG. 6 provides an isometric view of the thermal storage unit withmultiple vent closures open, according to some implementations.Therefore, FIG. 6 may represent a maintenance or failsafe mode ofoperation. As shown, the thermal storage unit also includes an innerenclosure 623. The outer surface of inner enclosure 623 and the innersurface of the outer enclosure define a fluid passageway through whichfluid may be conducted actively for dynamic cooling or passively forfailsafe operation.

Inner enclosure 623 includes two vents 615 and 617 which includecorresponding vent closures in some implementations (portions of ventdoor 613, in this example). In some implementations, vents 615 and 617define respective passages between an interior of the inner enclosure623 and an exterior of the inner enclosure. When the external ventclosure 603 is open, these two vents are exposed to the exterior of theouter enclosure as well.

As shown, vent 615 may vent heated fluid from the thermal storage blocksconducted by duct 619. The vent 617 may allow entry of exterior fluidinto the fluid passageway and eventually into the bottoms of the thermalstorage block assemblies via louvers 611 (the vent closure 609 mayremain closed in this situation). In some implementations, the buoyancyof fluid heated by the blocks causes it to exit vent 615 and a chimneyeffect pulls external fluid into the outer enclosure via vent 617. Thisexternal fluid may then be directed through louvers 611 due to thechimney effect and facilitate cooling of the unit. Speaking generally, afirst vent closure may open to output heated fluid and a second ventclosure may open to input external fluid for passive venting operation.

During passive cooling, the louvers 611 may also receive external fluiddirectly, e.g., when vent closure 609 is open. In this situation, bothvents 615 and 617 may output fluid from the inner and outer enclosures.

Vent door 613 in the illustrated implementation, also closes an input tothe steam generator when the vents 615 and 617 are open. This mayprevent damage to steam generator components (such as water tubes) whenwater is cut off, the blower is not operating, or other failureconditions. The vent 617 may communicate with one or more blowers whichmay allow fluid to passively move through the blowers even when they arenot operating. Speaking generally, one or more failsafe vent closure mayclose one or more passageways to cut off fluid heated by the thermalstorage blocks and reduce or avoid equipment damage.

When the vent door 613 is closed, it may define part of the fluidpassageway used for dynamic insulation. For example, the fluid movementsystem may move fluid up along one wall of the inner enclosure, acrossan outer surface of the vent door 613, across a roof of the innerenclosure, down one or more other sides of the inner enclosure, and intothe thermal storage blocks (e.g., via louvers 611). Louvers 611 mayallow control of fluid flow into assemblages of thermal storage blocks,including independent control of separately insulated assemblages insome implementations.

In the closed position, vent door 613 may also define an input pathwayfor heated fluid to pass from the thermal storage blocks to duct 619 andbeneath the vent door 613 into the steam generator to generate steam.

In some implementations, one or more of vent door 613, vent closure 603,and vent closure 609 are configured to open in response to anonoperating condition of one or more system elements (e.g.,nonoperation of the fluid movement system, power failure, water failure,etc.). In some implementations, one or more vent closures or doors areheld in a closed position using electric power during normal operationand open automatically when electric power is lost or in response to asignal indicating to open.

In some implementations, one or more vent closures are opened while afluid blower is operating, e.g., to rapidly cool the unit formaintenance.

Thermoelectric Power Generation

1. Problems to be Solved

Gasification is the thermal conversion of organic matter by partialoxidation into gaseous product, consisting primarily of H₂, carbonmonoxide (CO), and may also include methane, water, CO₂ and otherproducts. Biomass (e.g., wood pellets), carbon rich waste (e.g. paper,cardboard) and even plastic waste can be gasified to produce hydrogenrich syngas at high yields with high temperature steam, with optimumyields attained at >1000° C. The rate of formation of combustible gasesare increased by increasing the temperature of the reaction, leading toa more complete conversion of the fuel. The yield of hydrogen, forexample, increases with the rise of reaction temperature.

Turning waste carbon sources into a useable alternative energy orfeedstock stream to fossil fuels is a potentially highly impactfulmethod for reducing carbon emissions and valorizing otherwise unusedcarbon sources.

2. Thermoelectric Power Generation

Indirect gasification uses a Dual Fluidized Bed (DFB) system consistingof two intercoupled fluidized bed reactors—one combustor and onegasifier—between which a considerable amount of bed material iscirculated. This circulating bed material acts as a heat carrier fromthe combustor to the gasifier, thus satisfying the net energy demand inthe gasifier originated by the fact that it is fluidized solely withsteam, i.e., with no air/oxygen present, in contrast to the classicalapproach in gasification technology also called direct gasification. Theabsence of nitrogen and combustion in the gasifying chamber implies thegeneration of a raw gas with much higher heating value than that indirect gasification. The char which is not converted in the gasifyingchamber follows the circulating bed material into the combustor, whichis fluidized with air, where it is combusted and releases heat which iscaptured by the circulating bed material and thereby transported intothe gasifier in order to close the heat balance of the system.

Referring to FIG. 4 , in some example implementations, the thermalenergy storage structure 403 can be integrated directly with a steampower plant to provide an integrated cogeneration system 400 for acontinuous supply of hot air, steam and/or electrical power for variousindustrial applications. Thermal storage structure 403 may beoperatively coupled to electrical energy sources 401 to receiveelectrical energy and convert and store the electrical energy in theform of thermal energy. In some implementations, at least one of theelectrical energy sources 401 may comprise an input energy source havingintermittent availability. However, electrical energy sources 401 mayalso include input energy sources having on-demand availability, andcombinations of intermittent and on-demand sources are also possible andcontemplated. The system 403 can be operatively coupled to a heatrecovery steam generator (HRSG) 409 which is configured to receiveheated air from the system 403 for converting the water flowing throughconduits 407 of the HRSG 409 into steam for the steam turbine 415. In analternative implementation, HRSG 409 is a once-through steam generatorin which the water used to generate steam is not recirculated. However,implementations in which the water used to generate steam is partiallyor fully circulated as shown in FIG. 4 are also possible andcontemplated.

A control unit can control the flow of the heated air (and moregenerally, a fluid) into the HRSG 409, based on load demand, cost perKWH of available energy source, and thermal energy stored in the system.The steam turbine 415 can be operatively coupled to a steam generator409, which can be configured to generate a continuous supply ofelectrical energy. Further, the steam turbine 415 can also release acontinuous flow of relatively lower-pressure 421 steam as output tosupply an industrial process. Accordingly, implementations are possibleand contemplated in which steam is received by the turbine at a firstpressure and is output therefrom at a second, lower pressure, with lowerpressure steam being provided to the industrial process. Examples ofsuch industrial process that may utilize the lower pressure output steaminclude (but are not limited to) production of liquid transportationfuels, including petroleum fuels, biofuel production, production ofdiesel fuels, production of ethanol, grain drying, and so on.

The production of ethanol as a fuel from starch and cellulose involvesaqueous processes including hydrolysis, fermentation and distillation.Ethanol plants have substantial electrical energy demand for processpumps and other equipment, and significant demands for heat to drivehydrolysis, cooking, distillation, dehydrating, and drying the biomassand alcohol streams. It is well known to use conventional electric powerand fuel-fired boilers, or fuel-fired cogeneration of steam and power,to operate the fuel production process. Such energy inputs are asignificant source of CO₂ emissions, in some cases 25% or more of totalCO₂ associated with total agriculture, fuel production, andtransportation of finished fuel. Accordingly, the use of renewableenergy to drive such production processes is of value. Some ethanolplants are located in locations where excellent solar resources areavailable. Others are located in locations where excellent wind andsolar resources are available.

The use of electrothermal energy storage may provide local benefits insuch locations to grid operators, including switchable electricity loadsto stabilize the grid; and intermittently available grid electricity(e.g., during low-price periods) may provide a low-cost continuoussource of energy delivered from the electrothermal storage unit.

The use of renewable energy (wind or solar power) as the source ofenergy charging the electrothermal storage may deliver importantreductions in the total. CO₂ emissions involved in producing the fuel,as up to 100% of the driving electricity and driving steam required forplant operations may come from cogeneration of heat and power by a steamturbine powered by steam generated by an electrothermal storage unit.Such emissions reductions are both valuable to the climate andcommercially valuable under programs which create financial value forrenewable and low-carbon fuels.

The electrothermal energy storage unit having air as a heat transferfluid may provide other important benefits to an ethanol productionfacility, notably in the supply of heated dry air to process elementsincluding spent grain drying. One useful combination of heated airoutput and steam output from a single unit is achieved by directing theoutlet stream from the HRSG to the grain dryer. In this manner, a givenamount of energy storage material (e.g., brick) may be cycled through awider change in temperature, enabling the storage of extra energy in agiven mass of storage material. There may be periods where the energystorage material temperature is below the temperature required formaking steam, but the discharge of heated air for drying or otheroperations continues.

In some implementations thermal storage structure 403 may be directlyintegrated to industrial processing systems in order to directly deliverheat to a process without generation of steam or electricity. Forexample, thermal storage structure 403 may be integrated into industrialsystems for manufacturing lime, concrete, petrochemical processing, orany other process that requires the delivery of high temperature air orheat to drive a chemical process. Through integration of thermal storagestructure 403 charged by VRE, the fossil fuel requirements of suchindustrial process may be significantly reduced or possibly eliminated.

The control unit can determine how much steam is to flow through acondenser 419 versus steam output 421, varying both total electricalgeneration and steam production as needed. As a result, the integratedcogeneration system 400 can cogenerate steam and electrical power forone or more industrial applications.

If implemented with an OTSG as shown in FIG. 3 instead of therecirculating HRSG shown in FIG. 5 , the overall integrated cogenerationsystem 400 can be used as thermal storage once-through steam generator(TSOTG) which can be used in oil fields and industries to deliver wetsaturated steam or superheated dry steam at a specific flow rate andsteam quality under automated control. High temperature delivered by thebricks and heating elements of the system 403 can power the integratedheat recovery steam generator (HRSG) 409. A closed air recirculationloop can minimize heat losses and maintain overall steam generationefficiency above 98%.

The HRSG 409 can include a positive displacement (PD) pump 411 undervariable frequency drive (VFD) control to deliver water to the HRSG 409.Automatic control of steam flow rate and steam quality (includingfeed-forward and feed-back quality control) can be provided by the TSOTG400. In an exemplary example implementation, a built-in Local OperatorInterface (LOI) panel operatively coupled to system 400 and the controlunit can provide unit supervision and control. Further, thermal storagestructure 403 can be connected to a supervisory control and dataacquisition system (SCADA)) associated with the steam power plant (orother load system). In one implementation, a second electrical powersource is electrically connected to the steam generator pumps, blowers,instruments, and control unit.

In some implementations, system 400 may be designed to operate usingfeedwater with substantially dissolved solids; accordingly, arecirculating boiler configuration is impractical. Instead, aonce-through steam generation process can be used to deliver wet steamwithout the buildup of mineral contaminants within the boiler. Aserpentine arrangement of conduits 407 in an alternative once-throughconfiguration of the HRSG 409 can be exposed to high-temperature airgenerated by the thermal storage structure 403, in which preheating andevaporation of the feedwater can take place consecutively. Water can beforced through the conduits of HRSG 409 by a boiler feedwater pump,entering the HRSG 409 at the “cold” end. The water can change phasealong the circuit and may exit as wet steam at the “hot” end. In oneimplementation, steam quality is calculated based on the temperature ofair provided by the thermal storage structure 403, and feedwatertemperatures and flow rates, and is measured based on velocityacceleration at the HRSG outlet. Embodiments implementing a separator toseparate steam from water vapor and determine the steam quality based ontheir relative proportions are also possible and contemplated.

In the case of an OTSG implementation, airflow (or other fluid flow) canbe arranged such that the hottest air is nearest to the steam outlet atthe second end of the conduit. An OTSG conduit can be mountedtransversely to the airflow path and arranged in a sequence to providehighly efficient heat transfer and steam generation while achieving alow cost of materials. As a result, other than thermal losses fromenergy storage, steam generation efficiency can reach above 98%. Theprevention of scale formation within the tubing is an important designconsideration in the selection of steam quality and tubing design. Aswater flows through the serpentine conduit, the water first rises intemperature according to the saturation temperature corresponding to thepressure, then begins evaporating (boiling) as flow continues throughheated conduits.

As boiling occurs, volume expansion causes acceleration of the rate offlow, and the concentration of dissolved solids increases proportionallywith the fraction of liquid phase remaining. Maintaining concentrationsbelow precipitation concentration limits is an important considerationto prevent scale formation. Within a bulk flow whose average mineralprecipitation, localized nucleate and film boiling can cause increasedlocal mineral concentrations at the conduit walls. To mitigate thepotential for scale formation arising from such localized increases inmineral concentration, conduits which carry water being heated may berearranged such that the highest temperature heating air flows acrossconduits which carry water at a lower steam quality, and that heatingair at a lower-temperature flows across the conduits that carry thehighest steam quality flow.

Returning to FIG. 6 , various implementations are contemplated in whicha fluid movement device moves fluid across a thermal storage medium, toheat the fluid, and subsequently to an HRSG such as HRSG 409 for use inthe generation of steam. In one implementation, the fluid is air.Accordingly, air circulation through the HRSG 409 can be forced by avariable-speed blower, which serves as the fluid movement device in suchan embodiment. Air temperature can be adjusted by recirculation/mixing,to provide inlet air temperature that does not vary with the state ofcharge of the bricks or other mechanisms used to implement a thermalstorage unit. The HRSG 409 can be fluidically coupled to a steam turbinegenerator 415, which upon receiving the steam from the HRSG 409, causesthe production of electrical energy using generator 417. Further, thesteam gas turbine 415 in various embodiments releases low-pressure steamthat is condensed to a liquid by a condenser 419, and then de-aeratedusing a deaerator 413, and again delivered to the HRSG 409.

III. Steam Cracking System

Section III of the Detailed Description relates to the newly addeddisclosure of this continuation-in-part application. In the followingdescription, the thermal energy storage system, thermal storage medium,processes for use and variations thereon may be any of the range ofimplementations described throughout this continuation-in-partapplication, including in any combination with the variations discussedabove that were described in the aforementioned U.S. Pat. No.11,603,776.

Conventional Steam Cracking

Steam cracking is a common petrochemical process that breaks downsaturated hydrocarbons such as naphtha or ethane into smaller, usuallyunsaturated hydrocarbons. It is the primary industrial process inproducing lighter alkenes such as propylene and ethylene which are verycommon chemical building blocks for a variety of products such asplastics (polyethylene). For this reason, many petrochemical plants havea steam cracker unit on site. Steam cracking involves mixing a saturatedhydrocarbon with steam and exposing the mixture to very hightemperatures for very short periods of time in the absence of oxygen andsometimes in the presence of a catalyst. Reaction temperatures vary onthe desired product and the feedstock used, but are often above 850° C.Once the mixture has reached the reaction temperature, the mixture isquenched (cooled rapidly) to stop the reaction. The reaction residencetime is in the order of milliseconds and flow rates in the reaction zoneapproach the speed of sound. The process is mature and very sensitive tochange. The composition of the feedstock, the ratio of feedstock tosteam in the mixture, the cracking temperature, and residence timedetermine the chemical product produced by the reaction. The processoccurs in steam cracking furnaces. Because of the sensitivity of thereaction, there is not much drastic variation in the designs ofoperating steam cracking furnaces.

A conventional steam cracking process often includes two main zones: the“radiant zone” and a “convective” zone. The feed stream (often naphthaor ethane with steam) is cracked in the “radiant zone” of the reactorfurnace. This entails a highly preheated feed stream flowing at ratesthat approach the speed of sound, exposed to high-temperature radiantheat from hydrocarbon fuel-fired burners, with residence times on theorder of milliseconds. The burners supplying the radiant heatconventionally use some fuel (natural gas, fuel grade waste gas fromdownstream) with air. High flame temperatures are required to supplysufficient heat rates to heat the feedstock stream to reactiontemperature very quickly. The high-temperature flames heat reactiontubes containing the feedstock. Often, the radiant zone and convectivezone are vertically stacked upon one another with the radiant zone atthe bottom such that heat contained in the exhaust (flue) gas producedby burners in the radiant zone is recovered in the convective zone.

The furnace can take the form of a tower with flue gas temperaturesdecreasing with height as heat is recovered in the convective zone tomaximize exergetic efficiency. The radiant zone at the bottom containsburners that emit a large amount of heat. The radiant reaction tubespick up a fraction of the heat released by the burners for the crackingreaction. This fraction is referred to as the box efficiency. A boxefficiency may be under 50% such as 41%. In conventional systems, thecombination of the high temperature and the high heat rate requirementslead to low box efficiencies and consequentially large amounts of wasteheat. The unabsorbed heat in the radiant zone exits as high temperature(˜1100° C.) flue gas (the combustion products include H₂O, CO₂, andother emissions).

The flue gas of the combustion in the radiant zone burners are carriedup the plant or tower where the heat of the flue gas is absorbed in the“convection” (also referred to as “convective” in this writeup) zone ofthe steam cracking plant. The flue gas is typically cooled to as low atemperature as is practical (such as ˜100° C.) to maximize the use ofinput fuel, through an array of heat exchangers in the convection zone,before being released to the environment. An array of convective coilsor convection banks contain various streams that absorb heat for use inthe steam cracking reaction or for another use elsewhere in the plant.The thermal integration of these plants is generally very good, withoverall thermal efficiencies typically above 90%.

Conventionally, in order to minimize exergy loss, the streams to captureheat are ordered such that streams that are heated to lower temperaturesinteract with the cooler flue gas toward the top of the furnace, and thestreams that are heated to a higher temperature are located lower down,closer to the radiant zone where the flue gas is hottest.

An example flow diagram of a conventional steam-cracking furnace isdesignated generally by reference number 700 in FIG. 7 , depicting howthe streams heated in the convection banks are located based ontemperature. This is described in greater detail below.

Conventionally, the following may be heated in this order, with somevariations possible: the hydrocarbon feedstock (typically Naphtha orethane); boiler feedwater; dilution steam to be mixed with thefeedstock; high-pressure steam for use elsewhere in a plant; and thesteam/feedstock mixture. Often high-pressure steam is generated for usein a steam turbine to supply power for a plant. Export steam generatedmay be used for some other industrial process in the plant. There is alarge demand for export steam, since steam crackers are usually inpetrochemical plants with several other adjacent steam consumingprocesses. Waste heat is also recovered from the produced, cracked gas.

Once the feedstock reaches reaction temperature, the product is rapidlyquenched, typically in a transfer line heat exchanger, by high-pressureboiler feedwater or in a quenching header using quench oil. Whetherquench oil or water is used as a cooling medium for the quench, heat isfurther recovered from the heated-up quench fluid. When water is usedfor the quench, steam is generated and often sent to a steam drum wheregenerated steam can be further superheated in the convection zone. Thequenched cracked gas is often sent to a fractionator to separate out thedesired product from undesired or unconverted feedstock. Thisunconverted or undesired waste gas can be directed to the burners tosupply additional heat to the radiant zone.

Conventional Steam Cracking Furnace

FIG. 7 shows a simplified flowsheet example of a conventional steamcracking furnace 700. The figure shows a tower which is broken up into aflue stack exit at the top 701, 8 zones and a radiant zone. The 8 zonesare for illustrative purposes and represent sections of the convectivezone that have different temperature flue gas. Different streams arenumbered differently (S1, S2, etc.) and BFW refers to liquid boilerfeedwater. The temperatures and pressures of the streams as illustratedin the figure are based on an example, conventional processes and areprovided as example values to give a sense of how the streams in theconvective section operate. Example flow rates are omitted from thefigure for readability but may contribute to confusing temperatureswings of certain streams. Some streams shown have significantlydifferent flow rates than others.

At the bottom 702 of the furnace, hydrocarbon fuel 703 and combustionair 704 are brought together and combusted in the furnace. The flameicons represent side and bottom fired burners supplying heat to thefeedstock/steam stream S3 that exits the bottom left of convective zone8 at an example temperature and pressure of 596° C. and 2.29 bar. Thereaction tubes are not explicitly shown, but the S3 stream crossing theradiant zone is where the cracking reaction occurs to become cracked gasproduct stream S5 at example reaction temperature and pressure of,respectively, 865° C. and 1.67 bar. Although not shown, flue gasgenerated by combustion in the burners rises from the radiant zone toenter zone 8 where the flue gas may be at an example temperature of1120° C. The flue gas then travels up through the convection sectionfrom zone 8 to zone 1, where example flue temperatures at the bottom ofthe zone are 1120° C., 920° C., 780° C., 660° C., 420° C., 360° C., and170° C. After exiting zone 1, the flue gas may leave the stack at atemperature of 105° C.

Starting from the top left of zone 1, the pressurized hydrocarbonfeedstock (naphtha in this case) stream S1 enters the convection bank at65° C. and 3.7 bar in order to be preheated. S1 then exits at the bottomleft of zone 1 at a temperature of 113° C. and 3.5 bar. Not shown in thesimplified figure are the heat exchange coils or piping that make up theconvection bank where flue gas indirectly transfers heat to the streams.Entering in the middle left of zone 2, high pressure boiler feedwater(BFW) from the petrochemical plant's BFW system at 155° C. and 124.5 bargets preheated so as to enter the export steam drum at 265° C. and 121.7bar. Dilution process steam S2 enters the convection bank at the topleft of zone 3 at 190° C. and 5 bar and gets superheated to exit at thebottom left of zone 3 at 354° C. and 3.5 bar. Superheated dilution steamS2 is then mixed with the hydrocarbon feedstock S1 to form afeedstock/steam mixture S3 at 166° C. and 3.3 bar. S3 enters theconvection bank at the top left of zone 5 for further preheating. S3exits at the bottom left of zone 5 at 402° C. and 2.5 bar. S3 then getspreheated for a final time in zone 8, exiting zone 8 at 596° C. and 2.29bar. The hydrocarbon/steam mixture is raised to the highest temperaturepossible before undesired side reactions occur. The fully preheated S3is then sent to the radiant zone where the cracking reaction occurs. Theproduct stream S5 is cracked product gas at the reaction temperature of865° C. and 1.67 bar that contains the desired chemical product andunconverted feedstock and steam. S5 is immediately quenched in atransfer line heat exchanger (TLE) 705. Here high-pressure saturatedliquid boiler feedwater from the steam drum 706 indirectly exchangesheat with the hot product stream S5. The transfer line heat exchanger isconfigured such that the cracked gas product first exchanges heat withhigh-pressure boiler feedwater at near saturated liquid conditions. Thefeed water and the product gas S5 move through the heat exchanger in thesame direction such that the feed water gets vaporized into a saturatedvapor/liquid mix as it moves through the heat exchanger. Because thecooling water side of the heat exchanger is changing phases as heat isadded, the water/steam coolant remains at a constant temperature ofabout 325° C. throughout a large portion of heat exchange with thecracked gas. The water side may exit as saturated steam or superheatedsteam. S5 eventually exits the TLE at 427° C. and 1.55 bar. This crackedgas stream is quenched and ready to enter the next step in its chemicalprocessing, often fractionization. The generated steam exits the TLE toreturn to the steam drum providing heat to the steam drum. Saturatedsteam S4 at 325° C. and 120.2 bar exits the steam drum to enter zone 6for superheating. S4 exits zone 6 at 398° C. and 115.2 bar and thenenters a desuperheater 707 where boiler feed water (BFW) at a matchingpressure and lower temperature of 155° C. joins the stream. S4 then hasan increased flow rate but with a lower degree of superheat as thetemperature is reduced to 380° C. S4 then enters zone 7 to getsuperheated again so that S4 exits zone 7 at 520° C. and 112 bar. S4 isthen used elsewhere in the plant, likely in a steam turbine to generateplant or export power. Once expanded across the turbine, the steam mayeither be condensed to maximize power generation or not condensed suchthat lower pressure and temperature steam can be used elsewhere in theplant such as a source for dilution steam S2 entering the steam crackingfurnace at zone 3. The order of heat exchange in streams is designed tomaximize heat recovery of the waste heat from the burner exhaust flue.

Despite the exceptional heat recovery, this prevalent and importantprocess in systems currently in use emits a large amount of greenhousegas emissions. Given the global push for rapid decarbonization to slowthe damaging effects of climate change, several proposals to reduce thecarbon intensity of the steam cracking process have been explored andtested with some adapted. However, given the high level of plantwidethermal integration that is standard in operating steam crackingfurnaces, new technology is difficult to incorporate into existing,mature plant designs. A large part of the reason for this is thatexisting plants are designed around utilizing the heating duty of theflue gas from combustion in the radiant zone. Many sustainableinnovations in steam cracking involve reducing (or eliminating) flue gasemissions produced in burners in the radiant zone.

There is accordingly a demand for technology that replaces the reducedor eliminated heat duty from flue gas without contributing to carbonemissions and without being overly intrusive to the conventionalprocess. One of the more promising ways to reduce emissions and replaceheat otherwise supplied via hydrocarbon combustion is with electricity.Electrical energy can be converted to thermal energy at 100% efficiencyand at high temperatures that compete with flame temperatures.Additionally, electricity can be renewably generated without any directemissions. Renewable generation technologies such as solar PV and windturbines have seen a massive decrease in capital costs over the lastcouple of decades. Perhaps the largest downside of renewables such assolar and wind turbines is that they are intermittent resources. A solarfield will not generate when the sun is not out, and wind turbines willnot generate when the wind is not blowing. Many industrial processes,including steam cracking, run continuously, only shutting down forrequired maintenance. If intermittent renewable energy is to be used insuch processes, the generated energy must be stored when the energy isavailable but delivered on a continuous basis. Electrochemical storage,such as lithium-ion batteries, is one option for this. Another option isa thermal energy storage (TES) system as described throughout thisdisclosure. A thermal energy storage system may be able to charge withintermittent electricity while continuously or (optionally)intermittently discharging heat for a use. There are severaladvantageous integrations of a thermal energy storage system with bothconventional steam cracking processes and newer, sustainable steamcracking process improvements.

In the following description, it will be seen that TES (sometimesreferred to herein as “heat battery”) can be used as a supplementary hotgas generator to enable emission reducing technology in steam crackingprocesses. Such hot gas can replace flue gases and/or can preheatstreams before contacting flue gas in a convective section. Thisdisclosure also describes manners of TES integration with an electriccracker in a steam cracking process. Unless otherwise noted, FIGS. 8-15include all the same streams (S1, S2, S3, BFW, etc.) and zones asillustrated in the flow diagram of the conventional steam cracking plantof FIG. 7 . In addition, process components having the same two digitending (e.g., 705, 805, 905, etc.) are considered identical or verysimilar in function.

As mentioned above, in a conventional steam cracker, the feed stream iscracked in the radiant zone of the reactor furnace. The burnerssupplying the radiant heat are conventionally fired by a hydrocarbonfuel (such as natural gas or fuel grade waste gas from downstream) withair. High flame temperatures are required to supply sufficient heat veryquickly to the material stream. The flue gas from the combustion in theburners is released to the environment after recovering heat.

Several issues arise here. The high flame temperatures in the presenceof relatively high concentration of nitrogen gas from air leads to theformation of NOx, a strictly regulated emission that imposes hardlimitations on plant operations worldwide. Often, the flame temperatureis limited by concerns about NOx formation when air is used forcombustion air. Given the importance of heating rate in the radiantsection, a constraint on flame temperature can have a significantdisadvantage. In order to achieve a sufficient heating rate of thefeedstock, more fuel must be burned at a lower flame temperature. Asflame temperature increases, heating rate can be retained with far lessfuel given that radiant heat transfer rate scales with temperature tothe power of 4 (per the Stefan-Boltzmann law).

Secondly, the combustion of air and fuel creates flue gas with low CO₂compositions and high nitrogen compositions. This makes the isolationand capture of carbon dioxide for sequestration in this process verydifficult and energy intensive. Carbon capture and sequestration isbeing considered and adopted in several other high-temperatureindustrial processes as a way to reduce the carbon intensity of aprocess. Oxyfuel technology includes the external production of oxygen,in an air separation unit (ASU), so that the fuel is burned in anatmosphere with much lower concentrations of nitrogen, which inhibitsthe formation of NOx. Instead, the flue gas is composed of almost pureCO₂ and water, the primary stoichiometric products of combustion.

The flame temperature is also much higher since non-reactive nitrogenand argon are not consuming combustion energy. It is possible torecirculate flue gas to be mixed with a nearly pure oxygen and fuelmixture to control the flame temperature while maintaining a flue streamwith easily separable CO₂. This is a way to mimic conventional air-fuelburner conditions to minimize modifications to the existing plant. Ifthe product is captured, water can be easily condensed and knocked outof the stream, leading to a high purity stream of carbon dioxide to becaptured and transported, thus reducing emissions to the atmosphere.Oxyfuel combustion also leads to higher box efficiencies (efficiency ofheat transfer in the radiant zone) and smaller combustor units,resulting in dramatic decrease in flue gas volume compared toconventional fuel-fired furnaces.

Some disadvantages of oxyfuel burners are, first, that the flamecharacteristics change considerably due to the new chemical compositionof the flame. Heat and mass transfer as well as reaction kinetics aredifferent compared to the conventional case leading to new designs.Flame instabilities can also arise. Another is the electricity demand toproduce nearly pure oxygen in an air separation unit (ASU). It requiresa large amount of electricity to separate oxygen from air which can becostly for a facility. Finally, if retrofitting an existing steamcracking process with ox-fuel burners, there may be less flue gas than aconventional plant setup. This means that there is less heat availableto the convection section, meaning feedstock preheating and export,high-pressure steam production may suffer.

The present invention includes a thermal battery (heat battery) that canaddress these issues in a variety of ways. The first is replacing theduty of the reduced flue gas in the convective section. By directlysupplying hot gas that is generated by stored cheap grid electricity orintermittent renewables such as wind and solar, the plant can reap thebenefits without needing to replace the missing heat from the reducedflue gas heat. Additionally, in some implementations the thermal storagesystem may circulate any gas composition which may aid in recirculatingproduced flue gas at higher temperatures, which improves overall energyefficiency. For example, the heat battery could recirculate nearly pureCO₂ after water vapor is removed or the full flue stream of CO₂ andwater, maintaining a high CO₂ purity flue concentration in theconvection section exit stream while also using the recirculated flue tostabilize the flame.

In FIG. 9 , an example implementation of a thermal energy storage system(TES) 909 supporting the adoption of oxyfuel fired technology. An airseparation unit (ASU) 908 uses electricity to supply oxygen-enriched air(or pure oxygen) to the fuel burners 903. The fuel may be hydrocarbonand/or hydrogen. The heat battery or thermal energy storage system (TES)909 supplies heat in the form of hot gas S6 to the cracking furnace atthe burners in the radiant zone and/or just before entering theconvection section (zones 1-8). The hot gas may be injected into theburners in order to stabilize the flame. Although not shown in thefigure, the TES 909 may also preheat the oxygen and/or fuel prior toentering the burner to raise the flame temperature that is no longerlimited by the risk of NOx production.

Metallurgical constraints may still limit the flame temperature. The hotgas heated by the TES 909 may be recirculated CO₂ or flue gas from theexit of the convection section. Once the hot gas from the TES 909 isinjected into the furnace, the flue gas from combustion and the hot gascontinues up the convection zone of the furnace. The TES 909 maydischarge hot gas at specific temperatures and/or flow rates such thatthe combined flue gas stream mimics the heat transfer characteristics ofa conventional process. This enables the adoption of oxy-firedtechnology without a modification to the convection zone of aconventional steam cracking process. The combined flue and hot gasstream (S6 at the top of the furnace in the diagram) may be at atemperature of 105° C. at the outlet of the convection zone. In oneembodiment, the TES hot gas is recirculated as shown (stream S6), andthe composition of this stream S6 is nearly pure CO₂ and water vapor.The stream S6 may be cooled for the purpose of removing water vapor viacondensation (shown as water knockout 910 in FIG. 9 ). A portion of thenow nearly pure CO₂ stream may be exported as stream S7 at the top ofthe figure. This export CO₂ may be compressed in order to be transportedvia pipeline for commercial use such as carbonated beverage production,for enhanced oil recovery, or for geologic sequestration. The remainderof the stream may be recirculated back to the TES 909 to continue thecycle.

FIG. 10 shows a similar integration with an oxyfuel fired system of FIG.9 with the only change being the use of an electric booster heater 1011to further raise the temperature of the gas heated by the TES 1009 tohigher temperatures.

New heat recovery methods (e.g., high-emissivity coatings) have beendesigned in way that reduce fuel consumption and carbon emissions ofconventional steam-cracking furnaces by up to 30%. However, again thiscomes at the cost of a reduced convective section heat duty since thedesign aims at directing as much energy as possible to the process dutyof cracking in the radiant section. Another innovation that is beginningto be used is applying high-emissivity coating to the radiant zonereactor tubes. The coatings allow uniform emissivity over widetemperature ranges. This allows for more effective radiant heat transferfrom the flame to the process material which ultimately improves the boxefficiency. The advantage of this is that less fuel needs to be burnedin order to crack the same amount of process material. More heat fromthe combustion is absorbed by the radiant coils where the crackingreaction is occurring meaning that less energy is spent heating thefurnace refractory lining (thus lowering the exterior temperature of thefurnace and having less energy lost to the environment), and less energyis lost in the flue gas. The main advantage of this is lower fuelconsumption in the radiant section which reduces total plant emissions.Some other reported advantages are a higher ethylene yield, higherfurnace thermal efficiency, and increase in overall furnace performance.The reduced temperature of the furnace's refractory lining alsominimizes shrinkage and reduces maintenance. A disadvantage of thistechnology is that less heat exits with the flue gas stream.

As mentioned with the oxyfuel case, the convection sections (see zones1-8 in FIGS. 8-10 ) are conventionally designed to generatehigh-pressure steam and preheat the reaction feedstock material. As aresult, with this modification the flue gas contains less heat.Embodiments of the present invention can replace this heat in variousmanners. For example, hot gas heated by the thermal energy storagesystem (TES) may be injected in line with the flue stream from theradiant zone. This increases the total flue gas volume and matches thetemperature of the combined flue stream, to mimic the conditions of aconventional convection zone. This allows an existing steam crackingfurnace to lower fuel consumption in the radiant section withoutdiminishing the heat in the convection section. A thermal energy storagesystem according to the present disclosure can replace the heatconventionally supplied by burning hydrocarbon fuel. Since the TES isable to store heat derived from electrical energy that may be renewablysourced, direct carbon emissions can be reduced.

In another implementation, the TES or heat battery injects gas along therefractory linings. This allows for a uniform, cooler refractory walltemperature, decreasing heat losses from the furnace lining, improvingfurnace thermal efficiency and increasing lifetime in the refractory byminimizing hotspots and lowering temperature, while still providingenough gas to provide the designed amount heat to the steam and preheatcoils. An embodiment of the present invention may also be configuredsuch that the TES injects a variety of gas compositions, such as pureCO₂ (for oxyfuel case), recirculated flue gas (to minimize losses inexit stream), or air.

The above-described reduction in the amount of heat in the flue gasavailable in the convection section can result in lower production ofhigh-pressure steam, which can have significant impacts on the normaloperation of a petrochemical plant in which the steam cracking furnaceis located. Export, high-pressure steam generated can used in steamturbines which can generate electricity or mechanically drive therefrigeration compressors and/or the main compressors for the separationprocess of the cracked gas downstream. Export steam can also be used asa feedstock or heating agent in other petrochemical processes in thelarger plant. The current invention allows the process to achieve theenhanced energy and emissions savings of an improved design, by beingable to continuously supply high-pressure steam with stored intermittentrenewable electricity stored as heat, while realizing the benefits ofthe emission-reduction technologies discussed above (high-emissivitycoatings, oxyfuel combustion and/or the use of hydrogen fuel).

FIG. 8 shows a simplified example system of a thermal energy storagesystem (TES) 809 replacing heat from an efficiency improvement in theradiant zone. The conventional steam cracker may otherwise be the sameas shown in FIG. 7 . Less hydrocarbon fuel is burned and an electricallycharged thermal storage system continuously supplies hot gas S6somewhere in the radiant zone or at the bottom of the convection zone attemperatures and flow rates such that the combined flue and hot gasstream has the same temperature and flow rate of a conventional steamcracker with no sustainable innovations adopted. Although not shown, thehot gas heated by TES 809 may be heated to higher temperatures by anauxiliary electric resistive heater after discharge from the thermalstorage system and before injection to the steam cracking furnace.

The second way a heat battery or thermal energy storage system canaddress the issue is by leaving the existing steam cracker furnace thesame with a reduced heat duty in the convection section. The consequenceis that some streams may not be heated to sufficient temperatures. Thestreams to be further heated are directed to the TES system where theTES heats the streams to a sufficient temperature. In anotherimplementation, the TES heats streams to a higher temperature than waspossible in a conventional system. For example, superheated steam couldbe generated at a higher pressure or superheated to a higher temperaturefor advantages in power generation.

Another sustainable innovation in the steam cracking process is usingelectrically heated catalysis reaction tubes to drive the crackingreaction. Here, a preheated mixture of steam and hydrocarbon feedstockis directed to reactor tubes that are lined with a catalyst. Heat issupplied by running electric current through the tube materialgenerating heat to raise the feedstock mixture to reaction temperature.The reaction is then quenched as before to stop the reaction when thedesired product is produced. Since no fuel is burned in the radiantsection, there may be a missing demand to supply heat to preheat thefeedstock material and/or supply heat for steam generation. The thermalstorage system may fill this demand to minimize the effect on the otherplant processes that would otherwise depend on the recovered waste heat.As before with the reaction proceeding in the conventional radianttubes, there is a demand to maximize preheating in order to minimizecontinuous electrical heating duty in the electric cracker.

FIG. 12 shows an abstracted schematic of a heat battery or TES 1209replacing all the heat duty of a conventional convection zone (zones1-8). The TES 1209 supplies heat in the form of hot gas S6 such as airto a conventional convection zone. Instead of exiting to theenvironment, the heat or hot gas from the TES 1209 at the end of theconvection zone may be recirculated at a temperature higher than ambienttemperature to the TES 1209 to minimize waste heat lost to theenvironment. An electric steam cracker 1212 fulfills the heat duty ofthe “radiant zone” in a conventional process where preheated feedstockis subjected to rapid heating to cracking temperature before beingpromptly cooled or quenched. FIG. 12A shows the simplest processintegration where hot gas from the TES 1209 indirectly preheats allfeedstock components prior to cracking in an electric cracker reactor.FIG. 12B shows a more complex level of integration as a partialfulfillment of heat recovery steam generation of a conventional process.Conventionally, steam cracking processes have been designed to recoverthe large amount of heat contained in flue gasses from the hightemperature cracking reaction in the “radiant zone.” Often times, wasteheat is used to generate steam for use in another process or for powergeneration. In this process integration, high pressure boiler feedwaterwhich is ultimately used to quench the cracked product gas, is heated,in-line with feedstock components, to near saturated liquid conditionswith hot gas from TES units. The integrated system provides saturatedsteam in addition to quenched cracked gas. The process integration ofFIG. 12C shows an electrified, drop-in replacement of a conventionalsteam cracker. The process produces steam of the same quantity andconditions of the reference, conventional process. It takes thehigh-pressure saturated steam of the prior integration and superheats itin-line with the feedwater economizer and feedstock preheating. Theresulting product is high-pressure, superheated steam ready for powergeneration in a steam turbine. The heat and mass flow rates shown inFIGS. 12A-12C are exemplary only and are not limited to a specific steamcracking system.

FIG. 11 is the same heat battery integration process as that shown inFIG. 12 except that it includes the addition of an electric boosterheater 1111 to produce higher temperature gas than the TES 1109 alonemay be able to supply.

The TES may also be configured to replace all thermal energy in aconventional cracking furnace. Shown in FIG. 14 , the TES 1409 heatshigh temperature fluid S6 at temperatures sufficient for the crackingreaction otherwise occurring in the conventional radiant zone. Anoptional electric booster (not shown in FIG. 14 but designated byreference numeral 1311 in FIG. 13 ) may be used to further boost thetemperature of the heating fluid to higher temperatures than the thermalenergy storage system 1409 can provide. The hot fluid heated by thethermal energy storage system 1409 may follow a similar path of theconventional process where the highest temperature fluid first exchangesheat with the feedstock mixture to drive the cracking reaction beforecontinuing to exchange heat with successively lower temperature thermalloads. The heat transfer mode may be primarily convection as hot fluidsdirectly contact the reaction tubes. If the heating fluid is made up ofmolecules that can contribute to radiant heat transfer such as watervapor or CO₂, radiant heat transfer may be an additional mode of heattransfer. As shown in FIGS. 13 and 14 , the heating fluid S6 may berecirculated back to the thermal storage system after being sufficientlycooled in heat exchange. This allows for an increase in thermalefficiency over conventional systems as low temperature heat containedin the cooled hot gas is not vented to the environment and isrecirculated to the thermal storage system at a temperature aboveambient.

Another variation of a TES 1509 supplying all heat for the steamcracking process is shown in FIG. 15 . Here the thermal energy storagesystem 1509 has extra tubing where the preheated feedstock mixture readyfor cracking enters. The thermal energy storage system 1509 rapidlyheats the feedstock mixture primarily via radiation between the reactiontubing. The thermal storage medium such as solid metal, carbon orrefractory material is maintained at high temperatures by theintermittent charging of the TES. The drastic temperature differencebetween the temperature of the radiant reaction tubes and the storagemedium drives radiative heat exchange. In addition, hot fluid may becirculating through the thermal energy storage system. This may have aneffect of keeping the radiative surface of the storage medium at aconstant temperature to supply continuous radiative heat transfer. Thecirculating hot fluid S6 may exit the TES 1509 at some high temperatureand flow rate that may mimic the heating capabilities of flue gas inconventional systems. The hot fluid flows through the convection zonetransferring heat to all or some of the streams that would be heated ina conventional convection section. The hot fluid may only preheatfeedstock and steam for use in the reaction. The hot fluid may also heatboiler feedwater and additional steam for use elsewhere in another plantprocess or in a thermal power cycle such as a steam turbine. The nowcooled fluid stream exits the convection zone (used in an abstract sensehere for easy comparison; note that the heat transfer configuration maynot be performed in a traditional steam cracking furnace as shown in thediagram, but some other heat exchange configuration) where it may berecirculated back to the TES 1509 for reheating. Although not shown, anelectric booster heater may be used to elevate the temperature of thehot fluid to higher temperatures. Additionally, the radiant heattransfer inside the TES 1509 to the reaction tubes may also be boostedby electric booster heaters to supply heat at elevated temperatures oraid in supplying more uniform heat transfer across the reaction vessel.

FIG. 15A shows the system of FIG. 15 in which the export steam isprovided to a thermal power cycle for generation of electricity which isused to power the TES and/or may also be exported for some other use.

A thermal energy storage system can enable the adoption of new,sustainable technology in a conventional steam cracking process. Asmentioned, often part of the concern with adopting a new technology in asteam cracking facility is not how well the technology works, but whatconsequences can it have for adjacent processes designed around aconventional steam cracking process. As discussed above, the TES canreplace all or a portion of the heat otherwise supplied by the burningof fossil fuels. The TES can also integrate with adjacent plantprocesses in conjunction with its integration in the steam crackingprocess. FIGS. 16 and 17 show a simplified, yet more macroscopic,example of a TES integration to other plant components (thermal powergeneration cycles in these figures).

FIG. 16 shows an integrated system comprising a thermal energy storage(TES) system, electric cracker and thermal power cycle in which: the TESsystem supplies heat for feedstock preheating and steam generation; theelectric cracker converts preheated feedstock mixture into cracked gas;and the thermal power cycle generates electricity for the electriccracker. The lines with [Preheat] and [Steam generation] represent someheat exchange structure similar in function to the convection path inFIG. 12 . The hot gas from the TES passes through the heat exchangersbefore returning to the TES as cooled gas labeled in the figure at anexample temperature of 150 C. Exiting the upper heat exchanger ispreheated feedstock for entry into electrically heated catalysis tubes.Again, this resembles, in function, the process depicted in more detailin FIG. 12 . In FIG. 12 , superheated export steam (S4 exiting theprocess in FIG. 12 ) is generated by hot gases from the TES beforeexiting the convection zone of the cracking process as superheated steamat a temperature of 520° C. In FIG. 16 , an example path of thissuperheated steam is shown exiting to the right of the lower heatexchanger. The superheated steam is expanded across a steam turbinewhich generates power. The expanded stream may be condensed or may benon-condensed and used for some other process in the plant. This powermay be used to power the electrically catalytic cracking tubes.

FIG. 17 shows a more integrated view of the process depicted in FIG. 13where the TES supplies hot gas which is further raised in temperatureusing an electric booster heat in order to supply heat to both the steamcracking reaction and feedstock and export steam streams that are commonin conventional cracking processes. Again, the TES supplies hot gas atsome elevated temperature to an electric booster heater which raises thegas temperature further. The hot gas from the TES travels downwards (inthe Figure) first contacting the reaction tubing which may containcatalytic material where the steam cracking reaction takes place. Afterthe hottest temperature gas contacts the cracking tubes, the hot gascontinues through a series of heat exchangers to generate export steamand preheat the feedstock. The thermal power cycle shown in the upperleft portion of FIG. 17 depicts a TES system that provides hightemperature heat to steam generated in the quench cooling of the crackedgas. All generated export steam can be expanded across a steam turbinewhich generates electricity which may be used to power the electricbooster heater and/or exported to some other use.

To the extent a term used in a claim is not defined below, it should begiven the broadest definition persons in the pertinent art have giventhat term as reflected in printed publications and issued patents at thetime of filing. For example, the following terminology may be usedinterchangeably, as would be understood to those skilled in the art:

-   -   A Amperes    -   AC Alternating current    -   DC Direct current    -   DFB Dual Fluidized Bed    -   EAR Enhanced Oil Recovery    -   EV Electric vehicle    -   GT Gas turbine    -   HRSG Heat recovery steam generator    -   kV kilovolt    -   kW kilowatt    -   MED Multi-effect desalination    -   MPPT Maximum power point tracking    -   MSF Multi-stage flash    -   MW megawatt    -   OTSG Once-through steam generator    -   PEM Proton-exchange membrane    -   PV Photovoltaic    -   RSOC Reversible solid oxide cell    -   SOEC Solid oxide electrolyzer cell    -   SOFC Solid oxide fuel cell    -   ST Steam turbine    -   TES Thermal Energy Storage    -   TSU Thermal Storage Unit

Additionally, the term “heater” is used to refer to a conductive elementthat generates heat. For example, the term “heater” as used in thepresent example implementations may include, but is not limited to, awire, a ribbon, a tape, or other structure that can conduct electricityin a manner that generates heat. The composition of the heater may bemetallic (coated or uncoated), ceramic or other composition that cangenerate heat.

While foregoing example implementations may refer to “air”, includingCO₂, the inventive concept is not limited to this composition, and otherfluid streams may be substituted therefor for additional industrialapplications. For example but by way of limitation, enhanced oilrecovery, sterilization related to healthcare or food and beverages,drying, chemical production, desalination and hydrothermal processing(e.g. Bayer process.) The Bayer process includes a calcination step. Thecomposition of fluid streams may be selected to improve product yieldsor efficiency, or to control the exhaust stream.

In any of the thermal storage units, the working fluid composition maybe changed at times for a number of purposes, including maintenance orre-conditioning of materials. Multiple units may be used in synergy toimprove charging or discharging characteristics, sizing or ease ofinstallation, integration or maintenance. As would be understood bythose skilled in the art, the thermal storage units disclosed herein maybe substituted with other thermal storage units having the necessaryproperties and functions; results may vary, depending on the manner andscale of combination of the thermal storage units.

As used in the description herein and throughout the claims that follow,the meaning of “a,” “an,” and “the” includes plural reference unless thecontext clearly dictates otherwise. Also, as used in the descriptionherein, the meaning of “in” includes “in” and “on” unless the contextclearly dictates otherwise.

The recitation of ranges of values herein is merely intended to serve asa shorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein.

All methods described herein can be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples, or exemplary language (e.g.,“such as”) provided with respect to certain example implementationsherein is intended merely to better illuminate the exampleimplementation and does not pose a limitation on the scope of theexample implementation otherwise claimed. No language in thespecification should be construed as indicating any non-claimed elementessential to the practice of the example implementation.

Groupings of alternative elements or example implementations of theexample implementation disclosed herein are not to be construed aslimitations. Each group member can be referred to and claimedindividually or in any combination with other members of the group orother elements found herein. One or more members of a group can beincluded in, or deleted from, a group for reasons of convenience and/orpatentability. When any such inclusion or deletion occurs, thespecification is herein deemed to contain the group as modified thusfulfilling the written description of all groups used in the appendedclaims.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present application, the devices,members, devices, etc. described herein may be positioned in any desiredorientation. Thus, the use of terms such as “above,” “below,” “upper,”“lower,” “first”, “second” or other like terms to describe a spatialrelationship between various components or to describe the spatialorientation of aspects of such components should be understood todescribe a relative relationship between the components or a spatialorientation of aspects of such components, respectively, as the devicedescribed herein may be oriented in any desired direction.

In interpreting the specification, all terms should be interpreted inthe broadest possible manner consistent with the context. In particular,the terms “comprises” and “comprising” should be interpreted asreferring to elements, components, or steps in a non-exclusive manner,indicating that the referenced elements, components, or steps may bepresent, or utilized, or combined with other elements, components, orsteps that are not expressly referenced. Where the specification claimsrefer to at least one of something selected from the group consisting ofA, B, C . . . and N, the text should be interpreted as requiring onlyone element from the group, not A plus N, or B plus N, etc.

While the foregoing describes various example implementations of theexample implementation, other and further example implementations of theexample implementation may be devised without departing from the basicscope thereof. The scope of the example implementation is determined bythe claims that follow. The example implementation is not limited to thedescribed example implementations, versions or examples, which areincluded to enable a person having ordinary skill in the art to make anduse the example implementation when combined with information andknowledge available to the person having ordinary skill in the art.

What is claimed is:
 1. A steam cracking system for converting ahydrocarbon feedstock into cracked gas, comprising: a convection sectionconfigured to preheat a hydrocarbon feedstock and dilution steam and tomix the preheated hydrocarbon feedstock with the dilution steam toprovide a preheated mixture; a radiant section configured to convert thepreheated mixture into a cracked gas at high temperature; a coolingsection including at least one quench exchanger configured to quench thecracked gas; a thermal energy storage (TES) system configured to storethermal energy derived from electricity generated by an energy sourceand converting the electricity into heat for storage in a thermal energystorage medium and providing the stored heat to heat a fluid to atemperature in a target range; and a fluid movement system configured todirect the heated fluid into the steam cracking system at a hightemperature as either a sole heat source or a supplementary heat sourcein combination with a primary heat source.
 2. The steam cracking systemof claim 1, wherein the energy source is a variable renewable energysource having intermittent availability.
 3. The steam cracking system ofclaim 1, which includes an electric booster heater configured toincrease the temperature of the heated fluid prior to reaching the steamcracking system.
 4. The steam cracking system of claim 3, furtherincluding an export steam generation subsystem, wherein the steamcracking system is configured to provide heat to the export steamgeneration subsystem from both the cooling section and from the TESsystem.
 5. The steam cracking system of claim 4, further including athermal power cycle subsystem configured to receive steam from theexport steam generation subsystem and to generate electricity to beprovided to the electric booster.
 6. The steam cracking system of claim1, wherein at least a portion of the heated fluid exhausted from theconvection section is directed back as an input to the TES system forreheating.
 7. The steam cracking system of claim 6, wherein the heatedfluid is cooled to remove water vapor via condensation prior to input tothe TES system.
 8. The steam cracking system of claim 1, wherein thestorage medium comprises refractory material.
 9. The steam crackingsystem of claim 1, wherein: the primary heat source includes at leastone fuel burner configured to produce a flame from combustion ofhydrocarbon and/or hydrogen fuel with combustion air; and the fluidmovement system is further configured to inject the heated fluid alongfurnace refractory linings of the radiant section for radiant heattransfer from the flame to the preheated mixture.
 10. A steam crackingsystem for converting a hydrocarbon feedstock into cracked gas,comprising: a convection section configured to preheat a hydrocarbonfeedstock and/or dilution steam and to mix the preheated feedstock withthe dilution steam to provide a preheated mixture; a radiant sectionconfigured to be heated using an emission-reducing fuel and configuredto convert the preheated mixture into a cracked gas at high temperature;a cooling section including at least one quench exchanger configured toquickly quench the cracked gas; a thermal energy storage (TES) systemconfigured to store thermal energy derived from electricity generated byan energy source and converting the electricity into heat for storage ina thermal energy storage medium and providing the stored heat to heat afluid to a temperature in a target range; and a fluid movement systemconfigured to direct the heated fluid to one or both of the convectionsection and radiant section.
 11. The steam cracking system of claim 10,wherein the energy source is a variable renewable energy source havingintermittent availability.
 12. The steam cracking system of claim 10,wherein the emission-reducing technology includes one or more fuelburners configured to burn a fuel source that includes greater than 0.5%molecular hydrogen.
 13. The steam cracking system of claim 10, wherein:the emission-reducing technology includes one or more fuel burnersconfigured to burn a fuel source that includes greater than 0.5%molecular hydrogen in the presence of combustion air having a higheroxygen composition by volume than in ambient air; and the heated fluidfrom the TES system provides a make-up balance of heat duty required bythe convection section.
 14. The steam cracking system of claim 13,wherein the fluid movement system is further configured to stabilize aburner flame by supplying the heated fluid directly to the one or morefuel burners.
 15. The steam cracking system of claim 10, which includesan electric booster heater configured to increase the temperature of theheated fluid prior to reaching the convection section.
 16. The steamcracking system of claim 10, wherein the heated fluid exhausted from theconvection section is directed back as an input to the TES system forreheating.
 17. The steam cracking system of claim 16, wherein the heatedfluid is cooled to remove water vapor via condensation prior to input tothe TES system.
 18. The steam cracking system of claim 10, which furtherincludes a first heat exchanger configured to preheat the feedstockusing the heated fluid provided by the fluid movement system.
 19. Thesteam cracking system of claim 10, which further includes additionalheat exchangers configured to produce superheated dilution steam and/orother material streams heated in a conventional steam-cracking processusing the heated fluid provided by the fluid movement system.
 20. Thesteam cracking system of claim 10, wherein the storage medium comprisesrefractory material.
 21. A steam cracking system for converting ahydrocarbon feedstock into cracked gas, comprising: a preheating sectionconfigured to preheat a hydrocarbon feedstock and/or dilution steam, toproduce a preheated mixture of the hydrocarbon feedstock and thedilution steam; an electric cracker configured to convert the preheatedmixture into a cracked gas at high temperature; a thermal energy storage(TES) system configured to store thermal energy derived from electricitygenerated by an energy source and converting the electricity into heatfor storage in a thermal energy storage medium and providing the storedheat to the preheating section.
 22. The steam cracking system of claim21, further including a cooling section including at least one quenchexchanger configured to quench the cracked gas.
 23. The steam crackingsystem of claim 22, further including an export steam generationsubsystem, wherein the steam cracking system is configured to provideheat to the export steam generation subsystem from both the coolingsection and from the TES system.
 24. The steam cracking system of claim23, further including a thermal power cycle subsystem configured toreceive steam from the export steam generation subsystem and to generateelectricity to be provided to the electric cracker.
 25. The steamcracking system of claim 21, further including an export steamgeneration subsystem, wherein the steam cracking system is configured toprovide heat to the export steam generation subsystem from the TESsystem.
 26. The steam cracking system of claim 25, further including athermal power cycle subsystem configured to receive steam from theexport steam generation subsystem and to generate electricity to beprovided to the electric cracker.
 27. The steam cracking system of claim21, wherein the energy source is a variable renewable energy sourcehaving intermittent availability.
 28. The steam cracking system of claim21, which includes an electric booster heater configured to increase thetemperature of the heated fluid prior to reaching the convectionsection.
 29. The steam cracking system of claim 21, wherein the heatedfluid exhausted from the convection section is directed back as an inputto the TES system for reheating.
 30. The steam cracking system of claim29, wherein the heated fluid is cooled to remove water vapor viacondensation prior to input to the TES system.
 31. The steam crackingsystem of claim 21, which further includes a first heat exchangerconfigured to preheat the feedstock using the heated fluid provided bythe fluid movement system.
 32. The steam cracking system of claim 21,which further includes additional heat exchangers configured to producesuperheated dilution steam and/or other material streams heated in aconventional steam-cracking process using the heated fluid provided bythe fluid movement system.
 33. The steam cracking system of claim 21,wherein the storage medium comprises refractory material.
 34. A steamcracking system for converting a hydrocarbon feedstock into cracked gas,comprising: a thermal energy storage (TES) system configured to storethermal energy derived from electricity generated by an energy sourceand converting the electricity into heat for storage in a thermal energystorage medium; and a radiant section including radiant tubingconfigured to direct the preheated hydrocarbon mixture to the TES systemand to expose the tubing is to thermal radiation from the thermal energystorage medium to effectuate a cracking reaction.
 35. The steam crackingsystem of claim 34, further including a preheating section configured topreheat a hydrocarbon feedstock and/or dilution steam, to produce apreheated mixture of the hydrocarbon feedstock and the dilution steam.36. The steam cracking system of claim 35, further including a heatexchange system configured to provide thermal energy from the TES to thepreheating section.
 37. The steam cracking system of claim 34, furtherincluding a cooling section including at least one quench exchangerconfigured to quench the cracked gas.
 38. The steam cracking system ofclaim 37, further including an export steam generation subsystem,wherein the steam cracking system is configured to provide heat to theexport steam generation subsystem from both the cooling section and fromthe TES system.
 39. The steam cracking system of claim 38, furtherincluding a thermal power cycle subsystem configured to receive steamfrom the export steam generation subsystem and to generate electricityto be provided to the TES system.
 40. The steam cracking system of claim34, further including an export steam generation subsystem, wherein thesteam cracking system is configured to provide heat to the export steamgeneration subsystem from the TES system.
 41. The steam cracking systemof claim 40, further including a thermal power cycle subsystemconfigured to receive steam from the export steam generation subsystemand to generate electricity to be provided to the TES system.
 42. Asteam cracking system according to any of claims 37, 38, 39, 40 and 41,further including: a preheating section configured to preheat ahydrocarbon feedstock and/or dilution steam, to produce a preheatedmixture of the hydrocarbon feedstock and the dilution steam; and a heatexchange system configured to provide thermal energy from the TES to thepreheating section.
 43. The steam cracking system of claim 34, furtherincluding a fluid movement system configured to circulate a fluidthrough the thermal energy storage system and provide the circulatedfluid to the radiant section.
 44. The steam cracking system of claim 42,further including: an export steam generation subsystem, wherein thesteam cracking system is configured to provide heat to the export steamgeneration subsystem from the TES system; and a fluid movement systemconfigured to circulate a fluid through the thermal energy storagesystem and provide the circulated fluid to the export steam generationsubsystem and/or preheating section.
 45. The steam cracking system ofclaim 31, wherein the energy source is a variable renewable energysource having intermittent availability.
 46. The steam cracking systemof claim 34, which includes an electric booster heater configured toincrease the temperature of the heated fluid prior to reaching theradiant section.
 47. The steam cracking system of claim 34, wherein theheated fluid exhausted from the convection section is directed back asan input to the TES system for reheating.
 48. The steam cracking systemof claim 47, wherein the heated fluid is cooled to remove water vaporvia condensation prior to input to the TES system.
 49. The steamcracking system of claim 34, which further includes a first heatexchanger configured to preheat the feedstock using the heated fluidprovided by the fluid movement system.
 50. The steam cracking system ofclaim 34, which further includes additional heat exchangers configuredto produce superheated dilution steam and/or other material streamsheated in a conventional steam-cracking process using the heated fluidprovided by the fluid movement system.
 51. The steam cracking system ofclaim 34, wherein the storage medium comprises refractory material.